The auto-added `Expect: 100-continue` (for bodies >= 1024 bytes) decided
whether to withhold the request body based on raw socket readability via
select_read(). Over TLS, post-handshake records such as TLS 1.3 session
tickets make the socket readable without any HTTP response being
available, so the client withheld the body and then blocked reading a
response that never came, failing with `Failed to read connection`.
Decide based on whether a status line can actually be read within the
100-continue timeout instead: temporarily shorten the read timeout, try
to read the status line, and if none arrives, send the body and proceed
as usual (matching curl). This keeps the `100 Continue` and early
final-response paths working while no longer being fooled by TLS records.
Add a regression test using a raw OpenSSL server that never sends
`100 Continue`.
* Route proxy-enabled checks through is_proxy_enabled_for_host helper
In preparation for NO_PROXY support (#2446), centralize the proxy-enabled
decision in a single helper so the upcoming bypass logic can be added in
one place rather than to six divergent call sites. The helper's body for
now is identical to the existing condition; the host parameter is unused
until set_no_proxy() lands.
Refactored sites:
ClientImpl::create_client_socket
ClientImpl::handle_request (HTTP request rewrite)
ClientImpl::setup_redirect_client
ClientImpl::process_request (SSL is_proxy_enabled flag)
SSLClient::setup_proxy_connection
SSLClient::ensure_socket_connection
The two prepare_default_headers Proxy-Authorization injection blocks
(currently gated only on proxy auth credentials being set) are
intentionally not wrapped here. Doing so would change behavior in the
rare misconfiguration case where credentials are set without set_proxy,
so the gating is deferred to the NO_PROXY commit where it becomes
meaningful.
No behavior change. All 608 unit tests and the 22 squid-backed proxy
tests pass.
* Add detail::parse_proxy_url with control-char and scheme validation
Building block for the upcoming set_proxy_from_env (#2446). Parses
"http(s)://[user[:pass]@]host[:port][/...]" into a detail::ProxyUrl
struct.
Rejects:
- empty input
- any control character (< 0x20 or 0x7F), including CR/LF/NUL — these
would otherwise let a malicious env value inject extra header lines
into a CONNECT request or Proxy-Authorization header
- schemes other than http and https
- ports outside [1, 65535]
- malformed IPv6 host literals (validated via inet_pton(AF_INET6))
- non-numeric or trailing-garbage port strings
Notes:
- userinfo is split on the LAST '@' so passwords containing '@' are
preserved in the password field
- if no port is present, defaults to 80 (http) / 443 (https)
- integer parse goes through detail::from_chars to stay compatible
with -fno-exceptions builds
The helper has no callers yet; it lands consumer-side when
set_proxy_from_env arrives. All 608 unit tests pass.
* Add NO_PROXY parsing and matching helpers in detail namespace
Building blocks for the upcoming Client::set_no_proxy (#2446):
- NoProxyEntry / NoProxyKind: parsed list entry (wildcard, hostname
suffix, IPv4 CIDR, IPv6 CIDR)
- NormalizedTarget: pre-normalized form of the connection's target
host (lowercase, brackets stripped, trailing dot stripped, with
inet_pton already attempted)
- parse_no_proxy_entry / parse_no_proxy_list: token / list parsing.
Port-specific entries are rejected by design — cpp-httplib's other
host-keyed APIs (e.g. set_hostname_addr_map) are hostname-only, so
supporting host:port for NO_PROXY alone would be inconsistent.
- ipv4_in_cidr / ipv6_in_cidr: CIDR membership. IPv4 special-cases
prefix=0 to avoid the (1u << 32) shift UB. IPv6 uses byte-wise
memcmp plus a masked partial-byte compare.
- normalize_target: prepares the target host for matching. Routes
every IP literal through inet_pton so "127.0.0.1" vs
"127.000.000.001" vs decimal-form integers cannot be used to bypass
a NO_PROXY entry via alternate string forms.
- host_matches_no_proxy: matches a normalized target against an
entry list. Hostname suffix matching uses a dot-boundary rule so
"evilexample.com" does NOT match the entry "example.com". IPv4 and
IPv6 entries match only their own address family — IPv4-mapped IPv6
("::ffff:1.2.3.4") is not cross-matched against IPv4 entries.
These helpers have no callers yet; they land consumer-side in the
upcoming set_no_proxy / set_proxy_from_env commits. All 608 unit tests
pass.
* Add Client::set_no_proxy and wire NO_PROXY into proxy decision
Implements the user-facing half of #2446 (set_proxy_from_env follows in
the next commit). When a NO_PROXY pattern matches the target host, the
client now bypasses the configured proxy and the corresponding
Proxy-Authorization header is suppressed.
Public API:
- Client::set_no_proxy(const std::vector<std::string> &patterns)
Patterns: "*", hostname suffix (e.g. "example.com" or
".example.com"), IPv4/IPv6 CIDR (e.g. "10.0.0.0/8", "fe80::/10"),
or single IP literals. Replaces any previous list. Malformed
entries are silently dropped.
Internals:
- is_proxy_enabled_for_host now consults no_proxy_entries_, normalizing
the target through inet_pton so leading-zero or alternate-form IPs
cannot be used to bypass an entry.
- prepare_default_headers gates both Proxy-Authorization injection
blocks (basic and bearer) on is_proxy_enabled_for_host(host_).
Previously, Proxy-Authorization was sent whenever proxy auth
credentials were configured, even when the request was going direct
to the target. With NO_PROXY now in play, that path would leak
proxy credentials to the destination server — analog of the
redirect-leak class of bugs (cf. CVE-2023-32681 in Python requests,
GHSA-6hrp-7fq9-3qv2 in cpp-httplib).
- setup_redirect_client now takes the redirect target host as a
parameter and re-evaluates is_proxy_enabled_for_host against it.
no_proxy_entries_ is always copied to the redirect client so the
bypass policy follows across redirects. This is the cross-origin
leak surface that GHSA-c3h8-fqq4-xm4g lives in; centralizing the
decision through is_proxy_enabled_for_host removes the chance of
branch divergence.
- copy_settings copies no_proxy_entries_.
The slight behavior change for the rare misconfiguration "set
proxy_basic_auth without set_proxy" — Proxy-Authorization is no longer
sent in that case — is deliberate. The header has no addressee when
the proxy is unset.
All 608 unit tests and 22 squid-backed proxy integration tests pass.
* Add Client::set_proxy_from_env with httpoxy mitigation
Final user-facing piece for #2446. Reads proxy-related environment
variables and configures the client.
- HTTPS clients (SSLClient) read https_proxy / HTTPS_PROXY
- HTTP clients read http_proxy (lowercase only — see below)
- Both also read no_proxy / NO_PROXY
- Returns true if at least one variable was found and applied
The lowercase-only http_proxy rule mitigates httpoxy / CVE-2016-5385.
In CGI / FastCGI environments the uppercase HTTP_PROXY collides with
the HTTP_* namespace used to expose request headers, so a remote
attacker controlling the "Proxy:" header can inject a proxy URL.
cpp-httplib follows curl, Go, and Python requests in honoring only
the lowercase form. https_proxy/HTTPS_PROXY and no_proxy/NO_PROXY do
not have this problem because their names don't begin with HTTP_.
Scheme dispatch uses virtual is_ssl(): an SSLClient picks
https_proxy and a plain ClientImpl picks http_proxy. There is
intentionally no cross-scheme fallback — the two variables describe
different traffic.
set_proxy_from_env() reads getenv() synchronously and is documented
as "call once at startup" — concurrent setenv from other threads is
undefined.
All 608 unit tests pass.
* Add NO_PROXY behavior tests
27 black-box tests exercising the public Client API only (no detail::
calls, BORDER-friendly; no EXPECT_NO_THROW, -fno-exceptions-friendly).
In-process proxy mock + target server. Each test asserts which side
of the routing decision each request landed on, and what headers (in
particular Proxy-Authorization) the receiving side saw.
Coverage:
Suffix matching (dot-boundary rule)
- exact-host match
- subdomain match
- "evilexample.com" does NOT match "example.com" ← regression
guard for the classic NO_PROXY suffix-match pitfall
- "example.com.evil.com" does NOT match
- leading-dot pattern still matches the bare domain (Go/curl
convention)
- case-insensitive
- trailing-dot host normalization
Wildcard
- "*" bypasses everything
IP normalization
- exact IPv4 match
- "::1" matches "0:0:0:0:0:0:0:1" via inet_pton
- IPv4-mapped IPv6 ("::ffff:127.0.0.1") is NOT cross-matched
against an IPv4 entry
CIDR
- basic v4 in-cidr / not-in-cidr
- "0.0.0.0/0" (prefix=0; verifies no shift UB)
- bare IP treated as /32
- malformed prefix (/33) silently dropped → no NO_PROXY effect
Proxy-Authorization handling
- suppressed when NO_PROXY matches the target
- sent when NO_PROXY does not match
Backward compat
- default behavior unchanged when set_no_proxy is never called
Parsing edge cases
- port-specific entries ("host:port") rejected
- empty / whitespace tokens dropped
Cross-origin redirect (analog of GHSA-6hrp-7fq9-3qv2)
- redirect target in NO_PROXY → redirect leg goes direct, no
Proxy-Authorization carried over
set_proxy_from_env (Unix only — uses setenv/unsetenv)
- lowercase http_proxy applied
- uppercase HTTP_PROXY ignored (httpoxy / CVE-2016-5385)
- NO_PROXY-only env returns true and applies the bypass list
- CRLF in env value rejected (cf. CVE-2026-21428)
- empty env value treated as unset
635 tests (608 prior + 27 new) pass under both the regular and the
split builds.
* Document set_no_proxy and set_proxy_from_env in README
Adds two subsections under "Proxy server support":
- "Bypass the proxy for specific hosts (NO_PROXY)" — set_no_proxy,
pattern syntax, dot-boundary rule, IP normalization, limitations
(no port-specific entries, no v4-mapped v6 cross-match, replace
semantics).
- "Read proxy settings from the environment" — set_proxy_from_env,
which variables are read, the lowercase-only http_proxy rule with
an inline httpoxy / CVE-2016-5385 explanation, threading
expectations.
Documentation only. Closes the doc gap from #2446.
* Document NO_PROXY and set_proxy_from_env in cookbook c16-proxy
Replaces the now-incorrect Note at the bottom of c16-proxy ("cpp-httplib
does not read HTTP_PROXY...") with the actual API.
JA is the master per the project's translation workflow; the EN
translation lands in the same PR. Both pages remain `status: "draft"`
for normal review.
Adds two sections:
- Bypass the proxy for specific hosts (set_no_proxy):
pattern syntax, dot-boundary rule, case-insensitivity, IP
normalization via inet_pton, port-specific-entries unsupported,
malformed entries dropped.
- Read proxy settings from the environment (set_proxy_from_env):
which variables are read, lowercase-only http_proxy with an
inline httpoxy / CVE-2016-5385 explanation, threading caveat.
* Simplify NO_PROXY implementation per review
Apply seven post-implementation cleanups:
- Move ProxyUrl, ProxyEnvSettings and most helper forward declarations
below the BORDER. Only NoProxyKind/NoProxyEntry/NormalizedTarget stay
above (they are used as ClientImpl members or by inline cache state).
This shrinks the public header surface area considerably.
- Drop ProxyUrl::scheme: the field was write-only after parsing. Track
is_https as a local during parse_proxy_url and use it for the
default-port branch directly.
- Hoist the duplicate is_proxy_enabled_for_host(host_) gate in
write_request: the previous form had two adjacent gates bracketing
an unrelated end-server bearer-token block. Reordering puts the two
proxy-auth blocks together under a single gate.
- Drop the redundant trim_copy + empty-check inside parse_no_proxy_list:
detail::split already trims each token and skips empties, so the inner
work was dead code.
- Cache normalize_target(host_) on the client. host_ is const, so the
normalized form is invariant for the client's lifetime. The gate is
called up to 7 times per request when NO_PROXY is configured;
caching avoids repeating two heap allocations + two inet_pton calls
per request. Cross-host calls (only setup_redirect_client passing
next_host) still compute fresh.
- Trim narrative comments in setup_redirect_client and
set_proxy_from_env: replace WHAT-narration with single-line WHY
statements.
- Drop test comments that paraphrased their own test name.
All 635 unit tests pass under both the regular and split builds.
* Inline proxy URL parsing and env reading; drop intermediate structs
The previous design had two intermediate structs that existed only to
ferry parsed values between helper functions and the consuming method:
- detail::ProxyUrl: filled by parse_proxy_url, drained back into
proxy_host_ / proxy_port_ / proxy_basic_auth_* by set_proxy_from_env.
- detail::ProxyEnvSettings: bundle of two ProxyUrl + a NoProxyEntry
vector returned by read_proxy_env, drained by set_proxy_from_env.
Both bundles had exactly one producer and exactly one consumer. Drop
them and let the parsing flow directly into ClientImpl state:
- New private member ClientImpl::apply_proxy_url(url) parses a proxy
URL and, on success, assigns the result to proxy_host_, proxy_port_,
and proxy_basic_auth_*. Same validation as before (CRLF rejection,
scheme allowlist, port range, IPv6 bracket validation), same commit-
on-success ordering — the local variables are kept until every check
has passed so a malformed URL leaves no partial state.
- set_proxy_from_env now reads getenv() directly, dispatches between
https_proxy / http_proxy via virtual is_ssl(), and applies via
apply_proxy_url. NO_PROXY is parsed in place via parse_no_proxy_list.
Net effect:
- Two structs and two free helper functions removed (~150 lines of
declaration + body deleted).
- set_proxy_from_env body grows ~20 lines (still well under 50).
- Per-request hot path is unchanged (NoProxyEntry / NormalizedTarget
cache stays). Setup path is marginally faster (no intermediate
string copies through ProxyUrl / ProxyEnvSettings).
635 unit tests pass under both the regular and split builds.
* Trim doc comments to match the rest of httplib.h
The new code carried inline doc comments (15-line set_no_proxy block,
18-line set_proxy_from_env block, plus narrating comments inside parser
bodies, plus section dividers in the test file) that were heavy
compared to the rest of the codebase — neighboring setters like
set_proxy / set_proxy_basic_auth carry no doc at all, the test file
does not use sub-section dividers, and the README / cookbook already
document the behavior in detail.
Removed:
- Public-API doc blocks on set_no_proxy and set_proxy_from_env.
- Narrating comments inside parse_no_proxy_entry, normalize_target,
apply_proxy_url, host_matches_no_proxy that were just describing
the obvious code structure.
- Multi-line BORDER-rationale meta comments.
- In-test sub-section dividers ("// ---- Hostname suffix matching",
etc.) and per-class doc comments on the test fixtures.
- Test-side comments that paraphrased their own test name.
- Redundant ordering comments inside setup_redirect_client.
Kept:
- Security WHY comments (CRLF rejection, dot-boundary suffix matching,
httpoxy / CVE-2016-5385, GHSA-6hrp-7fq9-3qv2 analog, CVE-2026-21428).
- Regression-target WHY comments (UB shift on prefix=0).
- Non-obvious external knowledge (detail::split already trims).
635 unit tests still pass under both the regular and split builds.
* Add NO_PROXY tests covering edge cases found during PR review
Three regression guards added during review of an alternate NO_PROXY
implementation (PR #2449). All three pass on the current implementation
and surface bugs in the alternate one:
- BareIPv6LiteralMatchesIPv6Cidr: a host given as a bare IPv6 literal
(no surrounding brackets) must still be recognized as IPv6 for CIDR
matching. An implementation that only detects IPv6 when the host
string starts with '[' would split the host at the first ':' and
misclassify it as a hostname.
- TrailingDotOnEntryIsNormalized: trailing dots must be canonicalized
on BOTH sides — host and entry. An implementation that strips the
host-side trailing dot only would fail to match host "example.com"
against entry "example.com." because the substring lengths differ.
- ValidEntryWithSurroundingWhitespaceStillMatches: an entry with
leading/trailing whitespace must still match. An implementation
that feeds raw tokens directly to inet_pton would reject valid
CIDRs (" 10.0.0.0/8 ") because of the spaces.
635 unit tests pass.
* Unify IPv4/IPv6 CIDR matching into a single byte-buffer helper
Adopts the unified 16-byte address representation suggested by the
alternate NO_PROXY implementation in PR #2449. Both v4 and v6 entries
now share one storage type and one matcher; the v4/v6 distinction is
only the address-family flag and the max prefix length.
- detail::NoProxyEntry: replaces in_addr v4_net + in6_addr v6_net
with a single IPBytes net (std::array<uint8_t, 16>). v4 occupies
the first 4 bytes, v6 fills all 16.
- detail::NormalizedTarget: replaces in_addr v4 + in6_addr v6 with
a single IPBytes ip.
- Replaces detail::ipv4_in_cidr and detail::ipv6_in_cidr with one
detail::ip_in_cidr that takes the address, the network, the prefix
length and the family's max bits (32 for v4, 128 for v6). The mask
is constructed by the byte-fill approach from the previous v6
helper, which is straightforward to read and avoids the shift UB
that the v4 helper had to special-case.
- The NoProxyKind enum keeps IPv4Cidr / IPv6Cidr as separate values
so the match dispatch stays explicit and IPv4 entries cannot
accidentally cross-match an IPv6 target (the same address-family
isolation the previous code had).
Net change: -28 lines + -1 helper function. All 30 NoProxyTest cases
plus 643 unit tests pass under both the regular and split builds.
* Drop set_proxy_from_env per #2446 discussion
Per @unterwegi's feedback in #2446, environment variable handling
conflicts with cpp-httplib's long-standing policy of explicit
configuration (e.g. set_ca_cert_path requires explicit paths instead
of reading SSL_CERT_FILE / SSL_CERT_DIR). The NO_PROXY matching logic
is the genuinely tricky part worth keeping in the library; getenv
parsing is trivial and is left to the caller.
- Remove Client::set_proxy_from_env, ClientImpl::set_proxy_from_env,
and ClientImpl::apply_proxy_url
- Remove ScopedEnv test helper and env-driven NoProxyTest cases
- Replace the "Read proxy settings from the environment" docs with a
short snippet showing how to parse no_proxy and feed set_no_proxy()
- Keep set_no_proxy() and all NO_PROXY pattern matching intact
* docs: blend NO_PROXY env-var note into c16-proxy cookbook style
Match the granularity of the surrounding sections: imperative heading,
inline paragraph instead of a heavyweight callout, and a simpler getenv
snippet without the C++17 if-init.
* Skip digest 407 retry when target is bypassed by NO_PROXY
Before this fix, a NO_PROXY-bypassed origin that returns
407 Proxy-Authentication-Required with a Digest challenge would
trigger the same retry path the proxy uses, computing a
Proxy-Authorization header from proxy_digest_auth_* and sending the
user's proxy credentials directly to that (potentially hostile)
origin.
A 407 from a direct origin is semantically meaningless — RFC 9110
defines it strictly as a proxy response. Skip the retry when the
current target is not actually going through the proxy and let the
407 propagate to the caller unchanged.
Regression test BypassedTargetReturning407DoesNotLeakProxyDigest
Credentials reproduces the leak without this gate.
* Make set_no_proxy safe across redirects and keep-alive
Two correctness bugs that the dynamic NO_PROXY API exposed:
1. Multi-hop redirect through a bypassed host lost the proxy.
setup_redirect_client only copied proxy_host_/port and the proxy auth
credentials when is_proxy_enabled_for_host(next_host) was true. After
a chain like A (proxied) -> B (NO_PROXY-matched, direct) -> C, the
redirect client built for B had no proxy configured, so the further
B -> C hop went direct even when C should have been proxied. Copy the
proxy configuration unconditionally and let is_proxy_enabled_for_host
gate at send time. The next_host parameter is no longer needed and
removed from the signature.
2. Keep-alive socket reuse with a stale bypass decision. set_proxy() /
set_no_proxy() left the existing keep-alive socket open, so the next
request reused a socket pointed at the previous endpoint (proxy vs
origin) while write_request emitted the new request-line form
(absolute vs relative URL). Add invalidate_keep_alive_socket() and
call it from both setters; the helper handles the in-flight case by
deferring the close.
Regression tests MultiHopRedirectThroughBypassedHostKeepsProxy and
KeepAliveSocketInvalidatedOnSetNoProxy reproduce each bug without the
respective fix.
* Tighten NO_PROXY entry parsing
Three small parser fixes surfaced during code review:
- Accept bracketed IPv6 entries like "[::1]" and "[fe80::]/10". Users
coming from URL syntax naturally write the bracketed form; previously
it was silently rejected because inet_pton does not accept brackets
and the subsequent ':' check tripped.
- Reject malformed trailing-slash CIDRs like "127.0.0.1/" instead of
silently treating them as /32 (or /128). A typoed entry quietly
turning into a single-host bypass changes semantics with no
diagnostic.
- Delete detail::parse_no_proxy_list — leftover from the removed
set_proxy_from_env path, no longer called from anywhere.
New regression tests: BracketedIPv6EntryAccepted,
BracketedIPv6CidrEntryAccepted, TrailingSlashCidrIsRejected.
* Refactor: introduce disconnect() and remove invalidate_keep_alive_socket
Replace the repeated `shutdown_ssl + shutdown_socket + close_socket`
pattern with a single `disconnect(bool gracefully)` helper. Used by
`stop()`, the send_() peer-closed and epilogue branches, and the close
in process_request after a non-keep-alive response.
Drop `invalidate_keep_alive_socket()` — its body collapses to a
`lock + disconnect()` pair which is now inlined in `set_proxy()` and
`set_no_proxy()` directly.
Also simplify `setup_redirect_client`: drop the now-unused next_host
parameter and the verbose comment block; the per-target proxy decision
is re-evaluated at send time anyway.
Net -47 lines in httplib.h.
* Fix MultiHopRedirect test on Windows; trim NoProxyTest comments
The bypass leg redirected to "http://localhost:<port>/...", but on
Windows `localhost` resolves to ::1 first while the mock server is
bound to 127.0.0.1, causing the redirect leg to time out. Use the
literal 127.0.0.1 in the Location and switch the NO_PROXY entry to
match, so the test exercises the same multi-hop path on every
platform.
Also trim the heavier inline comments and EXPECT messages I added on
recent NoProxyTest cases so they match the surrounding test style.
* Consolidate NoProxyTest server boilerplate; drop hardcoded sentinel ports
Add a small ScopedServer helper to no_proxy_test that wraps the
bind/listen/thread/cleanup dance (~13 lines per server before). Use it
to rewrite the four big tests (Redirect, BypassedTarget407, MultiHop,
KeepAlive), shaving ~100 lines.
Also drop the hardcoded port-1 / port-80 sentinels that violated the
"new standalone tests MUST use bind_to_any_port" convention and risked
collisions across gtest shards: re-use existing dynamic ports
(target.port() / bypass_server.port()) instead.
Verified pass under 4-shard parallel run.
* Trim README NO_PROXY section to match surrounding granularity
The block had ballooned to 62 lines while neighboring subsections
(Authentication, Proxy server support, Range, Redirect) are 13-18 each.
Collapse to a single code example + one-line behavior summary; point at
the cookbook for the entry-form details, env-var parsing snippet, and
httpoxy note that used to live inline.
Adds Ubuntu and macOS CI jobs that build BoringSSL from source and exercise cpp-httplib's existing OpenSSL backend path (continue-on-error: best-effort). Makes SSLClientServerTest.TlsVerifyHostname backend-aware (BoringSSL is SAN-only per RFC 6125 §6.4.4). README notes BoringSSL as a best-effort variant with the C++14 and SAN-only caveats.
* Replace deprecated SecTrustCopyAnchorCertificates on macOS
SecTrustCopyAnchorCertificates was deprecated in macOS 13. Switch to
SecTrustSettingsCopyCertificates, iterating over the System, Admin, and
User trust domains to retain equivalent coverage of anchor certificates.
* Restrict Keychain cert loading to macOS
TARGET_OS_MAC is true on all Apple platforms including iOS, tvOS, and
watchOS, which caused the keychain enumeration path to be compiled on
iOS where SecTrustSettingsCopyCertificates is unavailable.
Narrow the auto-enable and the Security.h include guards to
TARGET_OS_OSX, and emit an explicit #error when the user defines
CPPHTTPLIB_USE_CERTS_FROM_MACOSX_KEYCHAIN on a non-macOS Apple platform,
directing them to use set_ca_cert_path() with a bundled CA file.
Addresses the iOS build break reported in #2454.
* Add iOS header parse check to CI
Run a cross-compile syntax check against the iOS SDK to catch
accidental use of macOS-only APIs or guards (e.g. TARGET_OS_MAC vs
TARGET_OS_OSX) that would silently break iOS builds. Also verify that
defining CPPHTTPLIB_USE_CERTS_FROM_MACOSX_KEYCHAIN on iOS fires the
expected #error.
iOS is not officially supported as a runtime target; this job only
guarantees the header stays parse-clean on iOS toolchains.
* The current implementation of "Server::stop()" doesn't throw an exception, so why not specify this explicitly?
* Adding the missing "noexcept" to the declaration
parse_header() applied decode_path_component() to every header value
except Location and Referer, after is_field_value() validation. Wire
sequences like %0D%0A passed the check and expanded into literal CR/LF
inside stored values, enabling response splitting, log injection, and
proxy smuggling. %3D/%2C/%3B also flipped Cookie and X-Forwarded-For
boundaries against WAFs inspecting the wire form.
RFC 9110 §5.5 specifies header values as opaque octets. Drop the
decoding and the Location/Referer special case (originally workarounds
for the same auto-decode misbehavior; redundant once decoding stops).
Applications that need URI semantics should call decode_uri_component()
or decode_path_component() on the result explicitly.
Add regression tests covering CRLF injection, %3D/%2C/%3B boundary
characters, UTF-8 and %uXXXX sequences, browser-style Referer URLs
containing %0A (issue #2033), and the explicit-decode migration
pattern.
* Make ThreadPool ctor exception-safe on partial thread creation
If std::thread construction throws partway through the ThreadPool
constructor (e.g., pthread_create returns EAGAIN under thread-resource
pressure), the partially-built threads_ vector would destruct joinable
std::thread objects, calling std::terminate(). Wrap the spawn loop and,
on failure, signal shutdown to the workers already created, join them,
and rethrow.
Adds a reproducer test in test_thread_pool.cc that interposes
pthread_create at link time to deterministically fail the second call,
gated to POSIX + exceptions-enabled builds.
Fix#2444
* Strip ASAN from test_thread_pool to coexist with pthread_create override
Linux libasan installs its own pthread_create interceptor; our in-binary
symbol override sits on top of it and corrupts ASAN's thread bookkeeping,
which surfaces as "Joining already joined thread" on the very first test.
Disable ASAN for this small unit-test binary -- ThreadPool memory behavior
is still exercised under ASAN by the main `test` binary.
strtoul silently accepts a leading "-" and wraps via unsigned
arithmetic, so chunk-size "-2" produced ULONG_MAX-1, bypassing the
ULONG_MAX guard and letting a client drive the server toward unbounded
allocation.
Replace strtoul with a manual hex parser that requires at least one hex
digit, detects size_t overflow per digit, and accepts only chunk-ext or
end-of-line after the digits (RFC 9112 §7.1).
When the upstream request to httpbingo.org transiently fails, cli.Get()
returns nullptr and the next line dereferences it (res->status / res->body),
producing a SEGV in std::string::begin() under ASan. Sibling templates in
the same file already use ASSERT_TRUE(res != nullptr); apply the same
guard to the four Get() call sites in KeepAliveTest so a flaky network
turns into a clean test failure instead of a crash.
The hosted windows-latest runner is migrating from VS 2022 to VS 2026
(NOTICE: windows-2025 -> windows-2025-vs2026 by 2026-05-12). The
hardcoded path C:\Program Files\Microsoft Visual Studio\2022\Enterprise
no longer exists on the new image, so vcvarsall.bat silently fails and
'cl' is not on PATH.
Resolve the install path via vswhere.exe (stable location, version
agnostic) and exit if vcvarsall.bat fails so future breakage surfaces
immediately instead of as a confusing 'cl not recognized' error.
The test referenced detail::can_compress_content_type, which lives below
the split BORDER in httplib.h and is therefore not visible to test.cc in
test_split / Windows-CMake builds. EXPECT_NO_THROW also expanded to a
try/catch that would not compile under -fno-exceptions. The OSS-Fuzz
reproducer in test/fuzzing/corpus already serves as the regression test
for #508087118 and is exercised by make fuzz_test.
When a glob like clusterfuzz-testcase-minimized-foo_fuzzer-* did not
match anything, bash passed the literal pattern through. The standalone
runner then tried to open it, tellg() returned -1, and the resulting
size_t cast (SIZE_MAX) crashed std::vector with length_error. This made
fuzz_test fail loudly during bisects to commits before a corpus file
landed. Filter each glob through a -f test so unmatched patterns are
silently skipped with a "(no XXX corpus)" notice, mirroring what was
already done for url_parser_fuzzer.
str2tag_core is recursive (one frame per character), so a long runtime
input such as a fuzzer-supplied Content-Type would overflow the stack.
Rewrite the runtime entry point str2tag() iteratively while keeping the
recursive constexpr str2tag_core for compile-time UDL evaluation. The
hash output is unchanged for all inputs.
Same root cause as #508342856 (fixed in 2d2efe4): an oversized
Content-Length value (here 4467440718547775) caused res.body.reserve()
to attempt a multi-petabyte allocation. The UBSAN fuzzer job surfaced
it as a std::bad_alloc-driven abort, while the ASAN job for #508342856
reported it as allocation-size-too-big. The payload_max_length_ cap
introduced in 2d2efe4 already addresses both.
A malicious or malformed server response with an enormous Content-Length
header (e.g. 20000000000) caused the client to call res.body.reserve(len)
with the untrusted value, triggering OOM before read_content's
payload_max_length_ check could take effect. Cap the pre-reservation
at payload_max_length_, since reading more than that is never useful.
* Restore getaddrinfo_a path with proper worker-completion wait (#2431)
5ebbfee dropped the Linux/glibc getaddrinfo_a branch entirely to avoid
the stack-use-after-free reported in #2431. That sidestepped the bug
but lost the asynchronous-resolution capability getaddrinfo_a is meant
to provide.
Bring the getaddrinfo_a branch back with the actual fix on the
cancellation path: after gai_cancel() — which is non-blocking and may
return EAI_NOTCANCELED while the resolver worker is still mid-operation
— call gai_suspend() with no timeout in a loop until gai_error() stops
returning EAI_INPROGRESS. Only then is it safe to destroy the
stack-local gaicb. freeaddrinfo() is also called on any partially
populated ar_result so that error paths do not leak.
This is the approach suggested in the issue body, with gai_suspend
substituted for the busy-poll over gai_error.
The issue-2431 reproducer test (run under ASAN with sinkhole DNS) is
unchanged and continues to drive the cancel path; it now exercises the
restored getaddrinfo_a code rather than the std::thread fallback.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
* Simplify getaddrinfo_a branch (idiomatic init, scope_exit, fewer comments)
- Value-initialize gaicb / sigevent / timespec with {} instead of memset
- Replace the two manual freeaddrinfo calls with a scope_exit guard, with
request.ar_result reset to nullptr on the success path to release
ownership to the caller (matches the addrinfo cleanup pattern used in
detail::create_socket and friends)
- Inline the single-call wait_for_request_done lambda
- Drop the (const struct gaicb *const *) cast — the array decays without
it under C++11
- Tighten the leading comment to the one load-bearing fact (#2431) and
the trade-off about pathological DNS waits; remove a stale claim that
the inner loop handles EAI_INTR (the loop checks gai_error, not the
gai_suspend return value)
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
---------
Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
* Add test for #2435 mmap::open with concurrent writer
Verifies that detail::mmap can open a file held open with GENERIC_WRITE
by another handle (e.g. an active log file). Currently fails on Windows
because CreateFile2 omits FILE_SHARE_WRITE.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
* Fix#2435: allow mmap to open files held open for writing
Add FILE_SHARE_WRITE to the share mode passed to ::CreateFile2 so
detail::mmap can open a file even when another process holds it open
with GENERIC_WRITE (e.g. an active log file). Without this, CreateFile2
fails with ERROR_SHARING_VIOLATION because the new opener's share mode
must permit the existing handle's access mode.
This brings the Windows path's behavior in line with the POSIX path
which uses ::open(O_RDONLY) and is unaffected by other processes'
write handles.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
---------
Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
The macos-latest runner is consistently slower than ubuntu-latest for
the ASAN+mbedTLS test binary, and SHARDS=2 still flakes there on the
ServerTest fixture's rapid bind/connect cycle against a fixed port.
Serialize fully (SHARDS=1) on macOS only; ubuntu mbedTLS stays at 2.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
With the close_notify mid-response fix and SHARDS=2 mitigation, the
mbedTLS legs run reliably on both ubuntu and macos. Drop the
continue-on-error escape hatch so future regressions actually break the
build.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Under ASAN+mbedTLS, the default 4-way sharding loads CI runners enough
that timing-sensitive ServerTest cases (Delete, PostMethod2, GetStreamed,
...) flake on what looks like first-request keep-alive reuse. Reducing
to 2 shards halves contention and historically stabilizes these on local
runs. The total test time goes up roughly 1.5x (still well under the job
budget) which is an acceptable trade for reliability.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
The mbedTLS backend's read() returned -1 with err.code = PeerClosed when
the peer sent close_notify, while OpenSSL and wolfSSL surface it as 0
(clean EOF). The result was that an SSL response without Content-Length
or chunked Transfer-Encoding — terminated by connection close — was
reported as "Failed to read connection" on mbedTLS, even though the
body had been fully delivered.
Translate PeerClosed into a return value of 0 to match the other
backends. This re-enables SSLTest.ResponseBodyTerminatedByConnectionClose
on mbedTLS.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
These tests reach out to external services (httpbin, YouTube, ...) and
flake on CI runners whenever those services are slow or unreachable.
The previous shard runner script silently masked these failures; now
that runs report them faithfully, default the filter to -*_Online.
Override via workflow_dispatch + the gtest_filter input to include
them when explicitly desired.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Skip SSLTest.ResponseBodyTerminatedByConnectionClose under
CPPHTTPLIB_MBEDTLS_SUPPORT until the close_notify-mid-response handling
is brought into parity with the OpenSSL and wolfSSL backends. The test
verifies a successful read past the server's close, which mbedTLS
currently reports as an I/O error.
Mark the mbedTLS matrix legs (ubuntu and macos) as
continue-on-error: true. Several timing-sensitive ServerTest cases
(PostMethod2, GetStreamed, Brotli, ...) flake under ASAN+mbedTLS in
ways unrelated to cpp-httplib code; isolating these into a non-blocking
slot keeps master green while the flakiness is investigated separately.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Add a libwolfssl entry to lsan_suppressions.txt to mirror the existing
libcrypto rule: the wolfSSL ECC subsystem caches per-handshake buffers
that are only freed at library shutdown, which the test binaries do
not perform. These are not leaks in cpp-httplib code.
Disable fail-fast on the ubuntu / macos / windows matrices so a failure
in one TLS backend does not cancel the others; with the runner now
detecting failures correctly, we want to see the full picture per run.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
These tests wrote to a hardcoded "/tmp/" path which does not exist on
Windows, causing the file write to silently fail and the subsequent
make_file_body / make_file_provider call to return zero-sized data.
Use a relative path under the test working directory instead so the
test runs identically on every platform.
Also dump the shard log when a shard's process exits non-zero even
when the gtest summary appears clean (e.g. sanitizer report after
the suite, or assertion-based abort) — previously such failures were
detected only via overall rc and showed no diagnostic output.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
The previous logic considered a shard "passed" if its log contained any
[ PASSED ] line, missing the case where some tests pass and some fail
(both [ PASSED ] N tests. and [ FAILED ] M tests, listed below:
appear in the gtest summary). Exit codes from the test binaries were
also ignored.
Now require both: an [ PASSED ] line, no [ FAILED ] line, and a
zero exit code. Track each shard's PID so wait can surface non-zero
exits.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
The Linux/glibc branch of detail::getaddrinfo_with_timeout used
getaddrinfo_a(GAI_NOWAIT) with a stack-local struct gaicb. On the
connection-timeout branch it called gai_cancel(), which is non-blocking
and may return EAI_NOTCANCELED -- in that case the resolver worker
thread is still alive and writes back to ar_result on the now-destroyed
stack frame after the function has already returned.
Drop the entire #elif _GNU_SOURCE && __GLIBC__ branch and let glibc
fall through to the existing std::thread + std::shared_ptr<State>
implementation that the file already uses for other Unix systems. That
path captures shared ownership in the resolver lambda, so the state
outlives the caller's frame whether or not the worker finishes in
time -- no stack frame is ever referenced after return.
The reproducer added in #2433 (issue-2431 repro CI job) goes from
hanging at job teardown to passing in ~25s with this change.
* Add reproducer for #2431 (getaddrinfo_a use-after-free)
On Linux/glibc, getaddrinfo_with_timeout() runs DNS asynchronously via
getaddrinfo_a(GAI_NOWAIT) using a stack-local gaicb. When gai_suspend()
hits the connection timeout, gai_cancel() is called and the function
returns immediately — but gai_cancel() is non-blocking and can return
EAI_NOTCANCELED, leaving the resolver worker thread alive and still
referencing the destroyed stack frame.
Adds three opt-in gtest cases (GetAddrInfoAsyncCancelTest.*) that
exercise the cancel path repeatedly. They are gated on Linux/glibc +
CPPHTTPLIB_USE_NON_BLOCKING_GETADDRINFO at compile time, and on the
CPPHTTPLIB_TEST_ISSUE_2431=1 env var at runtime, so a normal `make
test` run is unaffected.
Also adds a dedicated CI job (issue-2431-repro) and a Docker-based
local runner (test/run_issue_2431_repro.sh) that sinkhole UDP/53 so
the timeout branch is taken, and run the test under ASAN/LSAN. With
the bug present these runs are expected to fail; with a fix applied
they should pass.
Refs: https://github.com/yhirose/cpp-httplib/issues/2431
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
* Fix split build for #2431 reproducer tests
The new GetAddrInfoAsyncCancelTest cases call detail::getaddrinfo_with_timeout
directly. In split builds (make test_split) split.py moves the definition into
httplib.cc and strips `inline`, so the symbol is not declared in the public
httplib.h and test.cc fails to compile -- breaking the ubuntu/test-no-exceptions
CI jobs that the PR description says should be unaffected.
Add a forward declaration in test.cc, gated by the same #if as the tests
themselves, so it links against the split-build symbol without changing the
header-only build.
* Cap issue-2431 repro job at 5 minutes
The bug manifests as orphan getaddrinfo_a resolver workers that keep the
runner from completing job teardown -- the previous run had all steps
succeed in ~1m37s but then hung in "Cleaning up orphan processes" for
~57m before GitHub force-killed the job.
A job-level timeout-minutes makes the failure signal fast and predictable:
bug present -> killed at 5 min, bug fixed -> ~2 min pass. Step-level timeout
isn't enough since the hang is in post-job cleanup, not the test step.
* Enable ASAN detect_stack_use_after_return for #2431 repro
The bug is a textbook stack-use-after-return: a stack-local struct gaicb
is destroyed when getaddrinfo_with_timeout returns after gai_cancel()
yields EAI_NOTCANCELED, then the still-live resolver worker thread writes
back into the freed frame. ASAN's detect_stack_use_after_return is the
direct detector for exactly this pattern -- enabling it lets the failure
surface as a clear ASAN diagnostic during the test run instead of as an
orphan-process hang at job teardown.
* Revert ASAN detect_stack_use_after_return for #2431 repro
The option did not detect the bug in CI -- the resolver worker write
likely lands on the heap (via the gaicb's pai pointer) or happens after
the test process exits, neither of which stack-use-after-return can
catch. Roll back to relying on the job-level timeout: bug present ->
post-cleanup hangs ~8min then job-level timeout cancels at 10min total;
bug fixed -> job completes in ~2min.
* Switch issue-2431 repro to a delayed loopback DNS test fixture
The previous repro setup dropped UDP/53 outright, which made glibc's
resolver hang forever on every lookup -- the worker never actually
received a response and so never reached the buggy write-back path
that #2431 is about. As a result, neither the broken HEAD nor the
fix made any visible difference in CI: both produced "tests pass +
post-cleanup hangs ~10min" because the orphan resolver thread is a
structural property of *any* getaddrinfo path on a hung resolver,
not a property of the bug.
Replace the sinkhole with a small loopback test fixture
(test/dns_test_fixture.py, ~50 lines, stdlib only) that answers DNS
queries after a 3s delay -- longer than the test's 1s timeout. An
iptables NAT rule routes the test job's lookups to the fixture
without touching /etc/resolv.conf, so the rest of the runner's DNS
behaviour is unaffected.
With ASAN's detect_stack_use_after_return enabled, the worker's
late write-back into the destroyed gaicb stack frame is now caught
as a stack-use-after-return diagnostic, so the broken HEAD fails
fast at the test step (clear red) and the fix turns the same job
green in well under a minute.
Same fixture is wired into both the GitHub Actions job and the
docker-based test/run_issue_2431_repro.sh script, so local repro on
macOS and CI repro on Linux exercise the identical path.
---------
Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
* Fix#2427
* Use setarch -R on Linux to fix ASAN crash on WSL2
WSL2 uses high-entropy ASLR which conflicts with ASAN's shadow memory
requirements, causing the ASAN runtime to crash at startup. Running tests
via setarch -R (ADDR_NO_RANDOMIZE) disables ASLR for the test process,
allowing ASAN to initialize correctly.
Previously, dynamic threads exited as soon as their current task
completed and the queue was empty. This caused excessive thread
creation/destruction under bursty or long-lived workloads (e.g., SSE
streaming), degrading tail latency. Now dynamic threads loop back and
wait for CPPHTTPLIB_THREAD_POOL_IDLE_TIMEOUT (3s) before exiting,
allowing them to be reused for subsequent tasks.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
- Added `set_websocket_max_missed_pongs` method to configure unresponsive-peer detection.
- Updated README and documentation to clarify WebSocket limitations and features.
- Introduced tests for detecting non-responsive peers and ensuring responsive peers do not trigger timeouts.
The server listens on AF_INET6 only (::1), so the test fails:
[ RUN ] WebSocketIntegrationTest.SocketSettings
test/test.cc:17160: Failure
Value of: client.connect()
Actual: false
Expected: true
Fixes#2419.
Co-authored-by: Jiri Slaby <jslaby@suse.cz>
adds support for pre-existing `zstd::libzstd` which is useful for
projects that bundle their own zstd in a way that doesn't get caught by
`CONFIG`
Signed-off-by: crueter <crueter@eden-emu.dev>
* Remove 32-bit limitation
* Fix build problems
* Add 32-bit disclaimer and fix MSVC x86 warnings
- Move 32-bit warning to top of README with strong disclaimer
- Add static_cast<size_t> to fix truncation warnings on 32-bit MSVC
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
---------
Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>
- Update README for clarity and quick start instructions
- Refine default config.toml with hostname and base path
- Adjust index.md files for consistent heading levels
- Simplify CSS for code block styling and remove unnecessary theme switching
- Refactor SiteConfig to derive full base URL from hostname and base path
- Update MarkdownRenderer to remove light theme handling
- Implemented a search button in the header of each documentation page.
- Added a search modal that allows users to input search queries.
- Integrated a JavaScript search feature that fetches and displays results from a new `pages-data.json` file.
- Each documentation page now includes a search overlay for improved navigation.
- Updated the main JavaScript file to handle search logic, including result highlighting and navigation.
- Created a `pages-data.json` file containing metadata for all documentation pages to facilitate search functionality.
- Added a favicon link to all tour pages in the Japanese documentation.
- Updated navigation links to include SVG icons for Home and GitHub.
- Changed language button to include an SVG icon for better visual representation.
- Improved theme toggle button to use SVG icons for light and dark modes.
- Refactored the documentation build commands in the justfile for clarity and consistency.
* [CMake] New component MbedTLS
New component MbedTLS.
* Fix case
Fix case: HTTPLIB_REQUIRE_OPENSSL=OFF; HTTPLIB_REQUIRE_MBEDTLS=ON
* [CMake] Test target MbedTLS::tfpsacrypto
[CMake] Test target MbedTLS::tfpsacrypto.
* [CMake] Test MbedTLS::mbedx509
[CMake] Test MbedTLS::mbedx509.
* Revert "[CMake] Test MbedTLS::mbedx509"
This reverts commit 1d0b91f59a.
* Revert "[CMake] Test target MbedTLS::tfpsacrypto"
This reverts commit bf099f6264.
* Fix problem caused by the recent performance improvement
* wolfSSL support
wolfSSL support.
Partly solve https://github.com/yhirose/cpp-httplib/issues/2371. Only
meson is missing.
* Solve https://github.com/yhirose/cpp-httplib/issues/2361
Solve https://github.com/yhirose/cpp-httplib/issues/2361.
Apply `WARNING`.
* Fix variable
Fix variable.
* [CMake] Solve incompatibilities with loop
Solve incompatibilities with loop.
* Fix
Fix.
* Remove debug prints
Remove debug prints.
* [CMake] Fix bug
Prevent a bug aus the required and if available libraries are checked
independently from each other. A could be chosen in required but B could
be chosen in if available and everything would pass.
* Remove debug print
Remove debug print.
* Restore change
Restore change.
---------
Co-authored-by: yhirose <yuji.hirose.bug@gmail.com>
* Add initial documentations
* Update documentation for Basic Client and add WebSocket section
* feat: add a static site generator with multi-language support
- Introduced a new Rust-based static site generator in the `docs-gen` directory.
- Implemented core functionality for building sites from markdown files, including:
- Configuration loading from `config.toml`.
- Markdown rendering with frontmatter support.
- Navigation generation based on page structure.
- Static file copying and output directory management.
- Added templates for base layout, pages, and portal.
- Created a CSS file for styling and a JavaScript file for interactive features like language selection and theme toggling.
- Updated documentation source with new configuration and example pages in English and Japanese.
- Added a `justfile` target for building the documentation site.
* Add language/theme toggle functionality
- Created a new Japanese tour index page at docs/ja/tour/index.html
- Implemented navigation links for various sections of the cpp-httplib tutorial
- Added a language selector to switch between English and Japanese
- Introduced theme toggle functionality to switch between light and dark modes
- Added mobile sidebar toggle for better navigation on smaller screens
* WebSocket support
* Validate selected subprotocol in WebSocket handshake
* Fix problem with a Unit test
* Dynamic Thread Pool support
* Fix race condition in new Dynamic ThreadPool
* Remove macOS select() fallback
macOS has supported `poll` for a long time now, so there's no need for
the specific `select` code paths.
With this commit, we can successfully build on visionOS.
Signed-off-by: Adrien Gallouët <adrien@gallouet.fr>
* Fix coding style
Signed-off-by: Adrien Gallouët <adrien@gallouet.fr>
---------
Signed-off-by: Adrien Gallouët <adrien@gallouet.fr>
* Fix compilation on BoringSSL by replacing ASN1_TIME_to_tm
BoringSSL doesn't expose `ASN1_TIME_to_tm`.
This patch switches to using `ASN1_TIME_diff` to calculate `time_t`.
This is supported by OpenSSL, LibreSSL, and BoringSSL, and also avoids
the platform-specific `timegm` vs `_mkgmtime` logic.
Signed-off-by: Adrien Gallouët <adrien@gallouet.fr>
* Format code
Signed-off-by: Adrien Gallouët <adrien@gallouet.fr>
* Use detail::scope_exit
Signed-off-by: Adrien Gallouët <adrien@gallouet.fr>
---------
Signed-off-by: Adrien Gallouët <adrien@gallouet.fr>
* Correct sign comparison error with sk_X509_OBJECT_num
In some build configurations, sk_X509_OBJECT_num (from BoringSSL) returns a size_t. Comparing this directly against a signed int loop counter triggers -Werror,-Wsign-compare.
Instead, move the count into a local int variable so the compiler uses implicit conversion to ensure type consistency during the loop comparison.
* Update httplib.h
* Update httplib.h
Missed a s/int/decltype(count)
* Fix#2339
* Fix CI errors
* Fix Windows build error
* Fix CI errors on Windows
* Fix payload_max_length initialization in BodyReader
* Initialize payload_max_length with CPPHTTPLIB_PAYLOAD_MAX_LENGTH in BodyReader
* Update README and tests to clarify payload_max_length behavior and add no limit case
* Fix server thread lambda capture in ClientVulnerabilityTest
* Add C++ modules support
* Add module examples
* Missing semicolon
* Update GitHub Actions script and create a modules updating script
* Name the unused param
* Use the guarded/direct export of header approach
* Update CMakeLists.txt
Co-authored-by: Andrea Pappacoda <andrea@pappacoda.it>
* Update CMakeLists.txt
Co-authored-by: Andrea Pappacoda <andrea@pappacoda.it>
* Split scripts into split.py and generate_module.py
---------
Co-authored-by: Andrea Pappacoda <andrea@pappacoda.it>
* Add Tests for case sensitive hostname verfication
* Modify check_host_name to perform case insensitive comparisons during ssl hostname validation
---------
Co-authored-by: Tabor, Chris <chris.tabor@commscope.com>
Both APIs conceptually do the same thing: "use these CA certs for
verification." However, set_ca_cert_store() falls through to the else
branch in load_certs() where system certs are added to the user's
custom store, defeating the purpose of certificate pinning.
This change makes set_ca_cert_store() behave consistently with
set_ca_cert_path() by checking ca_cert_store_ before loading system
certificates.
Added test to verify system certs are not loaded when custom store is set.
Co-authored-by: Your <you@example.com>
* Resolve#2262
* Enhance request handling on Windows by adding early response check for large request bodies
* Enhance early response handling for large requests with long URIs on Windows
* Fix problem with 'windows without SSL`
* Fix payload limit enforcement for requests without Content-Length on Windows
- Enable MSG_PEEK on Windows (non-SSL builds) to detect payloads without Content-Length
- Only use MSG_PEEK when payload_max_length is set to a finite value to avoid blocking
- Use read_content_without_length for actual size checking to support any payload limit
- Set 413 Payload Too Large status before rejecting oversized requests
This fixes three test cases on Windows:
- RequestWithoutContentLengthOrTransferEncoding (no payload limit)
- NoContentLengthPayloadLimit (8-byte limit)
- NoContentLengthExceeds10MB (10MB limit)
* clang-format
* Ensure payload_max_length_ is respected for compressed payloads
* Fix Denial of service (DOS) using zip bomb
---------
Co-authored-by: Hritik Vijay <hey@hritik.sh>
On Windows cpp-httplib defines ssize_t, therefore applications needing
to define ssize_t for their own needs or are using libraries that do
require a means to avoid a possible incompatible redefinition.
Signed-off-by: Ralph Sennhauser <ralph.sennhauser@gmail.com>
To avoid surprises in the projects consuming the library, don't define
BUILD_SHARED_LIBS option ourselves but just use its value, if provided,
to define HTTPLIB_SHARED option which can be also set directly to
specify whether we should build static or shared library.
Closes#2263.
* Fix HTTP 414 errors hanging until timeout
* All errors (status code 400+) close the connection
* 🧹
---------
Co-authored-by: Wor Ker <worker@factory>
When the `SSLClient` is used to connect to a plain-HTTP server (which
can happen in clients due to some end-user misconfiguration) it can
return a failure from the `send()` call without setting the `Error`
reference to the corresponding error code. This can cause problems to
callers, that may expect that, when the check like this is passed on
the response:
```c++
if (res.error() == Error::Success)
```
then they can access the response contents with `res.value()`. When
`SSLClient`'s connection fails - the contents `unique_ptr` is not set
and an attemt to access it causes UB.
This change fixes the `SSLClient::create_and_connect_socket` method
making sure that, the `Error` value is set correctly when the
`is_valid()` check fails.
* Fix use of dangling references
When the resolve thread is detached, local variables were still used, which could lead to a program crash.
* Add test to verify dangling ref fix
* Add missing brace initialization
* Assert that the remaining fields are really zeroed
* Fix use of chrono literals
* Initialize start time for server
By initializing start_time_ for server, I hope to measure the time taken to process a request at the end maybe in the set_logger callback and print it.
I only see current usage in client with server retaining the inital min value
* Add test to verify start time is initialized
* Address review comments
* run clang format
* osx: fix inconsistent use of the macro `TARGET_OS_OSX`
Fixed the build error on iOS:
```
httplib.h:3583:3: error: unknown type name 'CFStringRef'
870 | CFStringRef hostname_ref = CFStringCreateWithCString(
```
Note, `TARGET_OS_OSX` is defined but is 0 when `TARGET_OS_IOS` is 1,
and vise versa. Hence, `TARGET_OS_MAC` should have been used, that is
set to 1 for the both targets.
* improve: non-blocking getaddrinfo() for all mac target variants
`TARGET_OS_MAC` should have been used, that is set to 1 for all other
targets: OSX, IPHONE (IOS, TV, WATCH, VISION, BRIDGE), SIMULATOR,
DRIVERKIT.
This is a follow-up to commit 4ff7a1c858,
which introduced new simplified build options and deprecated the old
ones. I forgot to also change the various get_option() calls,
effectively rendering the new option names useless, as they would not
get honoured.
On 32-bit Windows, meson setup fails with an unclear error:
meson.build:25:16: ERROR: Could not get define 'CPPHTTPLIB_VERSION'
The actual problem is that httplib.h #errors out.
Have the Meson logic explicitly check for a 32-bit host and warn or error,
matching the check in httplib.h. Phrase the Windows error in a way that
triggers WrapDB CI's unsupported architecture check.
The "cpp-httplib_" prefix of build options is now dropped, as Meson
build options are already namespaced for each project. The old names
remain as deprecated aliases for the new ones.
This new option automatically enables the new non-blocking name
resolution when the appropriate libraries are found, automatically
adding them to the list of required dependencies. It will gracefully
fall back to the old behaviour when no library is found.
This complements commit ea850cbfa7.
* Add proxy test on CI
* Add Brotli and Zstd dev packages to proxy test workflow
* Fix Docker Compose command for GitHub Actions compatibility
* Add proxy readiness check and netcat dependency
* Use netcat-openbsd instead of virtual netcat package
* Add proxy startup delay and debug logging
* Add test for multipart form data with boundary split
Add a test for multipart form data requests with a large header which
leads to a split inside the boundary because of the read buffer size
inside the SocketStream class.
* Fix bad request for multipart form data with boundary split
Fix a bad request (400) response for multipart form data requests with
a large header which leads to a split inside the boundary because of the
read buffer size inside the SocketStream class. The parse function
inside the MultipartFormDataParser wrongly erase the receive buffer if
it doesn't find the boundary inside the buffer during first call.
* Fix#2157
* Fix Windows build error: wrap std::max in parentheses to avoid macro conflict
- On Windows, max/min are often defined as macros by windows.h
- This causes compilation errors with std::max/std::min
- Solution: use (std::max) to prevent macro expansion
- Fixes CI build error: error C2589: '(': illegal token on right side of '::'
Fixes: error in coalesce_ranges function on line 5376
* Adds headers to multipart form data
Adds a `headers` field to the `MultipartFormData` struct.
Populates this field by parsing headers from the multipart form data.
This allows access to specific headers associated with each form data part.
* Adds multipart header access test
Verifies the correct retrieval of headers from multipart form data file parts.
Ensures that custom and content-related headers are accessible and parsed as expected.
* Enables automatic test discovery with GoogleTest
Uses `gtest_discover_tests` to automatically find and run tests, simplifying test maintenance and improving discoverability.
* Removes explicit GoogleTest include
* Refactors header parsing logic
Improves header parsing by using a dedicated parsing function,
resulting in cleaner and more robust code.
This change also adds error handling during header parsing,
returning an error and marking the request as invalid
if parsing fails.
* clang-format corrected
* Renames variable for better readability.
Renames the `customHeader` variable to `custom_header` for improved code readability and consistency.
* typo
* fix(parser): Limit line length in getline
Prevents potential infinite loop and memory exhaustion in
stream_line_reader::getline by enforcing max line length.
Signed-off-by: Ville Vesilehto <ville@vesilehto.fi>
* fix: increase default max line length to 32k
LONG_QUERY_VALUE test is set at 25k.
Signed-off-by: Ville Vesilehto <ville@vesilehto.fi>
* test(client): expect read error with too long query
Adds a test case (`TooLongQueryValue`) to verify client behavior
when the request URI is excessively long, exceeding
`CPPHTTPLIB_MAX_LINE_LENGTH`. In this scenario, the server is
expected to reset the connection.
Signed-off-by: Ville Vesilehto <ville@vesilehto.fi>
---------
Signed-off-by: Ville Vesilehto <ville@vesilehto.fi>
* Support zstd also via pkg-config
It doesn't always provide cmake config
* Find zstd with pkg-config also in non-required case
Code by @sum01, slightly modified
afunix.h uses types declared in winsock2.h, and so has to be included
after it. Including afunix.h first will result in a somewhat unhelpful
compilation error:
error C3646: 'sun_family': unknown override specifier
Signed-off-by: Piotr Stankiewicz <piotr.stankiewicz@docker.com>
* Add zstd support
* Add zstd to CI tests
* Use use zstd cmake target instead of ZSTD. Use cmake variable for found packages
* Add missing comment for HTTPLIB_REQUIRE_ZSTD
* Fix test.yaml rebase error
* Use zstd::libzstd target
* Add include and library paths to ZSTD args
* Run clang-format
* Add zstd to httplibConfig.cmake.in
By making the random engine thread_local, each thread now has its own
independent random sequence, ensuring safe concurrent access.
Additionally, using an immediately invoked lambda expression to
initialize the engine eliminates the need for separate static seed
variables.
* Wrap poll()/WSAPoll() in a function
Instead of using a macro for poll() on Windows, which breaks when the
implementation is compiled separately, add a detail::poll_wrapper()
function that dispatches to either ::poll() or ::WSAPoll().
* Build compiled library on Windows
Redirect tests fail using httpbin.org or nghttp2.org/httpbin. The
location header value contains a string representation of a Python byte
string (e.g., b'http://www.google.com/'), which results in a 404 error.
* Revert "Fix typo in meson.build (#2070)"
This reverts commit 5c0135fa5d.
* Revert "build(meson): automatically use poll or select as needed (#2067)"
This reverts commit 2b5d1eea8d.
* Revert "Make poll() the default (#2065)"
This reverts commit 6e73a63153.
* Remove select() and use poll()
- Replace is_readable() with wait_readable() and is_writable() with
wait_writable() in the Stream interface.
- Implement a new is_readable() function with semantics that more
closely reflect its name. It returns immediately whether data is
available for reading, without waiting.
- Update call sites of is_writable(), removing redundant checks.
* server_certificate_verifier extended to reuse built-in verifier
* code cleanup and SSLVerifierResponse enum clarification as per @falbrechtskirchinger comment
* cleanup
* clang-format
* change local var verification_status_ declaration to auto
* change local var verification_status_ to verification_status
* clang-format
* clang-format
---------
Co-authored-by: UrosG <uros@ub330.net>
Add include_httplib.cc to the main test executable (already done in
Makefile), and add include_windows_h.cc to the main test executable on
Windows to test if including windows.h conflicts with httplib.h.
* Add workflow_dispatch with Google Test filter
Add the workflow_dispatch trigger to the test.yaml workflow. Includes an
input for an optional Google Test filter pattern.
* Add OS selection to workflow_dispatch
* Fix wording
This CI workflow checks ABI compatibility between the pushed commit and
the latest tagged release, helping preventing accidental ABI breaks.
Helps with https://github.com/yhirose/cpp-httplib/issues/2043
Consider Content-Length and Transfer-Encoding headers when determining
whether to expect content. Don't handle the HTTP/2 connection preface
pseudo-method PRI.
Fixes#2028.
Modify for OpenVMS x86 C++. Make tests on OpenVMS currently not supported due to no cmake support.
Changes tested on OpenVMS clang C++ and Fedora & GCC
RFC-9110 '14.1.2. Byte Ranges':
A client can limit the number of bytes requested without knowing the
size of the selected representation. If the last-pos value is absent,
or if the value is greater than or equal to the current length of the
representation data, the byte range is interpreted as the remainder of
the representation (i.e., the server replaces the value of last-pos
with a value that is one less than the current length of the selected
representation).
https://www.rfc-editor.org/rfc/rfc9110.html#section-14.1.2-6
The testsuite checks for the exact size of the compressed content. The
exact size can change if the zlib library is using a different strategy.
In thise case using zlib-ng results in a slightly larger content leading
to a failure in the test.
Check that the compressed content is less than 10MiB which is a tenth of
the orignal content and proves that compression works.
Signed-off-by: Sebastian Andrzej Siewior <sebastian@breakpoint.cc>
* build(meson): bump minimum version to 0.62.0
This allows making some minor cleanups
* test(meson): fix SSLClientServerTest.* tests with OpenSSL 3.2.0
Since OpenSSL commit
<https://github.com/openssl/openssl/commit/342e3652c791bdb06e08abcc169b4456c83ccd00>,
the default X.509 certificate format generated with the `openssl req`
command has been changed to X.509 v3 from X.509 v1.
For some reason, this change breaks cpp-httplib's SSLClientServerTest.*
tests.
To fix the test failures, this patch passes the '-x509v1' flag instead
of '-x509' when OpenSSL 3.2.0 or newer is detected. To detect the
version of a command line utility, Meson 0.62.0 or later is required.
Fixes <https://github.com/yhirose/cpp-httplib/issues/1798>, but only for
the Meson build system.
* Renamed enable_server_host_verification to enable_server_hostname_verification and added Error::SSLServerHostnameVerification
* Add some Open SSL function calls
* Code cleanup
* Fix#1431
This patch is necessary to build cpp-httplib in Crashpad, itself in
Chromium, using BoringSSL. Details at [1].
The fixes include:
- Library version check: tolerate BoringSSL as an alternative to
OpenSSL 3.
- Don’t call `OPENSSL_thread_stop`, which is not in BoringSSL.
- Use `SSL_get_peer_certificate` (deprecated in OpenSSL 3), the old
name for `SSL_get1_peer_certificate`, because the new name is not in
BoringSSL.
- Call `SSL_set_tlsext_host_name` directly instead of making an
`SSL_ctrl` call that BoringSSL does not support. The feared
-Wold-style-cast warning that occurs when buidling with OpenSSL is
not triggered in BoringSSL.
[1] https://chromium.googlesource.com/crashpad/crashpad/+/1a62a0182557c89494676c06611f1ca731bcb2db
The test used the hardcoded long value for 64 bit machines even on 32
bit ones, leading to test failures. With this patch the max long length
is obtained using std::numeric_limits<long>::max(). Thanks to q2a3z for
the hint!
Fixes: https://github.com/yhirose/cpp-httplib/issues/1795
* New function SSLServer::update_certs. Allows to update certificates while server is running
* New function SSLServer::update_certs. Added unit test
* avoid memory leaks if linked with static openssl libs
---------
Co-authored-by: CEU\schielke <Rainer.Schielke@heidelberg.com>
* New function SSLServer::update_certs. Allows to update certificates while server is running
* New function SSLServer::update_certs. Added unit test
---------
Co-authored-by: CEU\schielke <Rainer.Schielke@heidelberg.com>
Release builds result in the following warning because `content_length` param was used only inside asserts:
1> cpp-httplib\httplib.h(4933,45): warning C4100: 'content_length': unreferenced formal parameter
* Windows has WSAAccept() which will create sockets inheriting flags from
the server socket
* Linux has accept4() which has a flags argument supporting SOCK_CLOEXEC
* Implement string divider to replace splitter
* Divide query string in half
* Add a test case for query values containing the '=' character
* Add test cases for string divider
* Fix warnings
* Move httplibConfig.cmake.in to cmake dir
Just makes more sense to put it there I suppose.
* Cmake install README & License
Seems to make sense since you might already do this as a package
manager, or an end user might want them anyways.
The locations are just based on standard Linux locations using
GNUInstallDirs, so it should be sane on other machines too.
using lambda expression as Handler in set_error_handler will cause ambiguous.
Template forwarding can forward HandlerWithResponse to the correct overloading function
* Unimportant cleanup of FindBrotli
Some whitespace, removal of an unused var, and add a comment about
the missing version support
* Fix incorrect var in FindBrotli
Not much to say, it was just the wrong one. Not sure how that happened,
maybe a holdover from when I did an overhaul at some point..
* Tiny useless edit to FindBrotli
Just a little tweak to how I was postfixing those -static strings to the
lib names. Mostly pointless..
* Simplify some FindBrotli code
Nothing much, just reducing redundant stuff & a cleanup of a comment.
* Ignore PkgConf in FindBrotli if looking for static
As per the issue mentioned in this comment, static PkgConf support
is broken upstream. After testing, I found it'll just accept shared
even if you try to find static, so I'm merely disabling that feature
for this FindBrotli module.
That said, you can still get the static libs if you have them installed,
but PkgConf will be ignored even if found in favor of a regular
find_library call. Otherwise you'd end up with shared libs even if you
ask for static (with PkgConf installed).
TLDR: actually fail correctly when static libs aren't found when PkgConf
thought they were.
* Reorder cmake docs a bit
Just wanted to group the more related build options together.
Also removed a pointless reference to the old reasoning for the required
min ver since it's 3.14 now anyways.
* Fix outdated cmake comment
We don't use Git to find the version string anymore.
Just updated to match what it's actually used for now.
* Group options and build-tree vars in Cmake
Doesn't really change anything, I just wanted to clean these up a bit.
* Fix how we set HTTPLIB_IS_USING_XXX vars in Cmake
Prevents us acidentally using libs when the user didn't want them
actually used. This could happen if they set the option to OFF but their
own project itself is using the lib, thus we'd find and use it anyways.
Ref #1602 to see an example of this already happening before.
This is merely apply that kind of fix to all 3 of our deps, instead of
just OpenSSL.
* Minor formatting/comment change to Cmake
Pointless, but these things were bothering me..
For very busy servers, the internal jobs queue where accepted
sockets are enqueued can grow without limit.
This is a problem for two reasons:
- queueing too much work causes the server to respond with huge latency,
resulting in repetead timeouts on the clients; it is definitely
better to reject the connection early, so that the client
receives the backpressure signal as soon as the queue is
becoming too large
- the jobs list can eventually cause an out of memory condition
* Fix: Query parameter including query delimiter ('?') not being parsed properly
* Add details::split function with and without m argument to allow split parameters with/without counter
* Revert changes in SplitTest.ParseQueryString
* Fix readability warnings
Did not fix readbility-qualified-auto, will do a separate pull request
* Revert changes where meaning is lost
* Revert some style changes
The exact circumstances when this false positive is triggered are quite
tricky to reproduce, but it happened reproducibly with g++ 13.1 and 13.2 in
a close-source SW I'm working on. The fix even improves performance by a
very tiny bit: There is no need to copy the std::smatch, having a const
reference is enough.
Just as a side note: -Warray-bounds seems to cause trouble in other
projects, too, so e.g. the Linux kernel has disabled since June 2022.
* ClientImpl: Connection=close header control moved from process_request to send_
* Connection=close header control moved from send_ to handle_request
* SSLClient::connect_with_proxy error handling improved
* to_string definition added for Error::ProxyConnection
* Comment improvement
---------
Co-authored-by: akinelden <akin.elden@gmail.com>
* Fix successful decompress reported as Error::Read
Streams less than 4096 bytes are sometimes reported as failed reads because stream_.avail_in is not reduced to 0. The next iteration of the loop finds `prev_avail_in == strm_.avail_in` and return false. `ret = inflate(...)` returns Z_STREAM_END on the first iteration of the loop indicating that inflate is finished. This fix prevents the second iteration of the loop from failing.
* Fix successful decompress reported as Error::Read
- Add unit tests for raw deflate that illustrates the decompression failure when there are extra trailing bytes
GoogleTest, starting with vesion 1.13.0, requires C++14 to build. This
patch enables C++14 if GoogleTest 1.13.0 or newer is detected when
compiling the tests with Meson, making it possible to use new GTest
versions.
You can find GoogleTest's release notes at
<https://github.com/google/googletest/releases/tag/v1.13.0>.
We already detect OpenSSL in our tree for another project, but don't want to
link httplib against OpenSSL or with SSL support.
Allow us to `set(HTTPLIB_IS_USING_OPENSSL FALSE)`.
Removed multiple old-style (C) casts and replaced them with the
appropriate _cast's. This makes httplib a better citizen inside projects
that are compiled with all warnings enabled.
Unfortunately one warning remains as a result of invoking an
OpenSSL macro (at least on Linux), that would have to be fixed
upstream.
Also fixed a few casts for invocations of setsockopt.
setsockopt takes a const void* for the value pointer, not a char*.
Well, except on Windows ...
Co-authored-by: Andre Eisenbach <git@4ae.us>
This allows disabling the use of C++ exceptions at CMake configure time.
The value is encoded in the generated httplibTargets.cmake file and will
be used by CMake projects that import it.
* Explicitly #include <utility> for use of std::move
* Move not copy Logger arg from Client to ClientImpl
* Move not copy, set_error_handler Handler to lambda
* Remove null statement in non-empty if/else block
I guess it was a relic from a time before the other statement was added.
---------
Co-authored-by: Daniel Boles <daniel.boles@voltalis.com>
* Reuse gtest on the system
Try to use gtest on the system if found. Avoid using recent CMake
features.
* Set CMP0135 only when using FetchContent
* Add /bigobj option for MSVC
* Support also cmake between 3.14 and 3.20
Older versions provided only GTest::Main target, not currently used
gtest_main. Provide backward compatibility also to old cmake versions.
* Remove redundant variable checking
---------
Co-authored-by: Jiwoo Park <jiwoo_90@naver.com>
* Support loading system certs from Keychein on MacOS
* review improvements: add deps to meson.build and improve conditional expressions in cmake
* fix tabs
* fix tabs
* review improvements
* fix after review
* additionally load root certs from the system root keychain
* cmake fix
* fix
* small refactoring
* small refactoring
---------
Co-authored-by: Sergey Kazmin <sergey.kazmin@kaspersky.com>
* Add test/CMakeLists.txt to enable testing with CTest
Add HTTPLIB_TEST option
Downlaod GoogleTest source using FetchContent module
Generate cert files to test httplib with OpenSSL
* Generate cert2.pem with a new certificate request
* Use the latest GoogleTest library
* add support for requests with both MultipartFormDataItems and ContentProviders
* rework implementation
* use const auto & and fix offset calculation
* fix zero items
* snake case variables
* clang-format
* commonize get_multipart_content_provider, add Put() with MultipartFormDataProviderItems
* fix linker multiple definition error
* add test MultipartFormDataTest.DataProviderItems
* Add EINTR and EAGAIN judge for accept
* Add EINTR signal tests
* Cancel win32 and win64 compile on signal unittest
Co-authored-by: yukun.yu <yukun.yu@alibaba-inc.com>
* Move next job in task queue rather than copy
* Notify waiting thread after unlocking mutex
* Add unit test for TaskQueue
* Don't use C++14 feature in test code
* handle socket options for UNIX socket same as others
* set FD_CLOEXEC by default
* invoke `socket_options` callback if set
* Offer Client info even on UNIX socket based Server
HTTP Request header "REMOTE_PORT" contains client process id if possible
when Server works on UNIX socket.
* retrigger checks
* retrigger checks
* add support macOS
Co-authored-by: Changbin Park <changbin.park@ahnlab.com>
* SocketStream need to check connectivity for writability.
When the stream is used for SSE server which works via chunked content
provider it's not possible to check connectivity over writability
because it's wrapped by DataSink. It could make the server stalled, when
the provider wants to only keep connection without send data and certain
amount of clients consumes entire threadpool.
* add unittest for SocketStream::is_writable()
SocketStream::is_writable() should return false if peer is disconnected.
* revise broken unittest ServerTest.ClientStop
DataSink could be unwritable if it's backed by connection based. Because
it could be disconnected by client right after enter centent provider.
Co-authored-by: Changbin Park <changbin.park@ahnlab.com>
Release 0.11 broke backwards compatibility, meaning that different
cpp-httplib versions are compatible with each other only if the major
and minor version numbers are the same.
This patch reflects this in the build systems.
See #1209 for some more context.
* httplib.h
add multipart formdata for PUT in addition to POST as some REST
APIs use that.
Factor the boundary checking code into a helper and use it from
both Post() and Put().
* test/test.cc
add test cases for the above.
* Add support UNIX domain socket
* `set_address_family(AF_UNIX)` is required
* add unittest for UNIX domain socket
* add support UNIX domain socket with abstract address
Abstract address of AF_UNIX begins with null(0x00) which can't be
delivered via .c_str() method.
* add unittest for UNIX domain socket with abstract address
Co-authored-by: Changbin Park <changbin.park@ahnlab.com>
* Add get_socket_fd method to Client and ClientImpl, add according unit test
* Change name get_socket_fd to get_socket
* Change name get_socket to socket
Co-authored-by: ata.yardimci <ata.yardimci@erstream.com>
* ssize_t redefinition on Windows - int/int64 vs long/long long
* Define ssize_t as __int64 for _WIN64, not long long
Co-authored-by: iamttaM <9880090+oculusbytes@users.noreply.github.com>
* resolve problem: http server can't send file large than 2GB.
add unit test for http server send large file.
add /bigobj compile option to msvc x64.
* disable unit test "ServerLargeContentTest" due to out-of-memory on GitHub Actions.
- Enable THREADS_PREFER_PTHREAD_FLAG to use -pthread where supported
- Remove low-level compile features (closes#1272)
- Remove unneeded DESTINATION options where possible
Thanks to abf3a67dd0 the use of python3
isn't required anymore to configure the build, so I moved the
find_program('python3') inside the "if compile" block.
This makes it possible to configure cpp-httplib on systems where python
isn't available with tools like muon: https://sr.ht/~lattis/muon/
* Add large data transfer test
* Replace `SSL_read` and `SSL_write` with `ex` functions
* Reflect review comment
* Fix return value of `SSLSocketStream::read/write`
* Fix return value in the case of `SSL_ERROR_ZERO_RETURN`
* Disable `LargeDataTransfer` test due to OoM in CI
Meson only runs required targets. The key_encrypted_pem and
cert_encrypted_pem targets added in 020b0db090
and 8191fd8e6c weren't added to the list
of targets required by the test target, so the generation of the
encrypted certs was skipped, resulting in the failure of
BindServerTest.BindAndListenSeparatelySSLEncryptedKey.
* meson: fix regression that broke extracting version
In commit 33f67386fe the code that
heuristically parsed the version broke due to the version being moved
around into a more easily accessible define.
While we are at it, pass the exact path of httplib.h to un-break usage
as a meson subproject. This was broken in commit
8ecdb11979 which checked the return code
of trying to get the version; it was always broken, but formerly failed
in silence and resulted in no version number.
* meson: use the compiler builtins to extract the version from the header
As a convenient string define, it is now possible to ask the
preprocessor what the version of cpp-httplib is. This can be used from
meson too, in order to avoid encoding C++ file structure into python
regexes.
A pkg-config file was previously installed only if cpp-httplib was being
built as a compiled library.
Since architecture-independent .pc files
can exist in /usr/share/pkgconfig, it can be useful to install one even
when installing the header-only version (for example, it could be used
by third party projects to easily find out if cpp-httplib is installed
and its version, using something like Meson's `dependency()` or CMake's
`pkg_check_modules()`).
The change makes the Meson build behave a bit more like the CMake one,
as it also always installs a CMake Config file, but here the pkg-config
file gets installed to the correct architecture-independent directory
(`datadir` represents /usr/share on Linux and simiar systems).
Lastly, I made some minor cleanups.
This change is based on RFC7230, § 3.5 'Message Parsing Robustness': "Although the line terminator for the start-line and header fields is the sequence CRLF, a recipient MAY recognize a single LF as a line terminator and ignore any preceding CR."
* Fix#1041
* Fixed problem with is_socket_alive
* Adjust the way to check if the sockt is still alive.
* Revert "Adjust the way to check if the sockt is still alive."
This reverts commit 6c673b21e5.
* Adjust is_socket_alive according to the code review
* Allow to specify server IP address
* Reimplement in set_hostname_addr_map
* Add tests for set_hostname_addr_map
* Fix tests after implement set_hostname_addr_map
* SpecifyServerIPAddressTest.RealHostname typo
This integrates the "main" test suite (test/test.cc) in Meson.
This allows to run the tests in the CI with the Meson-built version of
the library to ensure that nothing breaks unexpectedly.
It also simplifies life of downstream packagers, that do not have to
write a custom build script to split the library and run tests but can
instead just let Meson do that for them.
* Full Meson support
cpp-httplib can be now built with Meson even in compiled library mode.
The library is built with LTO, supports OpenSSL, zlib and Brotli,
and the build system also generates a pkg-config file when needed.
Compared to the CMake file this one is quite small (more than five times
smaller!), and maintaining it won't be an issue :)
* meson: automatic versioning
In order to test the split version (.h + .cc via split.py):
- Added a test_split program in the test directory whose main purpose is
to verify that it works to compile and link the test case code against
the split httplib.h version.
- Moved types needed for test cases to the “header part” of httplib.h.
Also added forward declarations of functions needed by test cases.
- Added an include_httplib.cc file which is linked together with test.cc
to verify that inline keywords have not been forgotten.
The changes to httplib.h just move code around (or add forward
declarations), with one exception: detail::split and
detail::process_client_socket have been converted to non-template
functions (taking an std::function instead of using a type parameter for
the function) and forward-declared instead. This avoids having to move
the templates to the “header part”.
When using the split version of httplib.h the templated implementation
of e.g. Client::set_connection_timeout ends up in httplib.cc and
therefore results in a linker error since the needed template
specialization has not been instantiated. Fix this by moving the
implementation of template methods into the part that ends up in
httplib.h after the split.
Fixes#1008.
The RedirectToDifferentPort.Redirect test assumes that port 8080 and
8081 are available on localhost. They aren’t on my system so the test
fails. Improve this by binding to available ports instead of hardcoded
ones.
- Added shebang and made the script executable.
- Added help text.
- Added -o/--out argument for specifying output directory.
- Added -e/--extension argument for specifying file extension of the
implementation file.
- Made the script find httplib.h next to split.py instead of the current
working directory. This makes it possible to call the script from
another directory.
- Simplified code structure slightly.
- Improved variable naming to follow Python conventions.
* Add header-only Meson support
This allows users to call `dependency('httplib')` and have the include
directory automatically configured
* Rename `httplib` to `cpp-httplib`
* Fix virtual call in ClientImpl::~ClientImpl()
This fixes a warning in clang tidy:
> Call to virtual method 'ClientImpl::shutdown_ssl' during
> destruction bypasses virtual dispatch
ClientImpl::~ClientImpl() calls lock_socket_and_shutdown_and_close()
that itself calls shutdown_ssl(). However, shutdown_ssl() is virtual
and C++ does not perform virtual dispatch in destructors, which results
in the wrong overload being called.
This change adds a non-virtual shutdown_ssl_impl() function that is
called from ~SSLClient(). We also inline sock_socket_and_shutdown_and_close()
and removes the virtual call in ~ClientImpl().
* Inline and remove lock_socket_and_shutdown_and_close()
The function only has one caller.
* Fix client.cc code, since res.error() without operator overloading causing error in Xcode
* Add unit test to check new error to string with operator overloading
* Add inline as requested in code review comment
* Special function to encode query params
* Fix #include <iomanip>
* Added unescaped charsets to encode_query_param
* Unit tests for encode_query_param
Add unit test for issue #682 fixed in PR #728, which does not contain
the test of its own.
The test creates a fake SSL server, inherited from SSLServer, which
does not create an SSL context. When an SSL client attempts to send it
a request, it gets a timeout error. Prior to PR #728, the client would
wait indefinitely
Co-authored-by: Michael Tseitlin <michael.tseitlin@concertio.com>
* ssl-verify-host: fix verifying ip addresses containing zero's
If the subject alternate name contained an ip address with an zero
(like 10.42.0.1) it could not successfully verify.
It is because in c++ strings are null-terminated
and therefore strlen(name) would return a wrong result.
As I can not see why we can not trust the length returned by openssl,
lets drop this check.
* ssl-verify-host: add test case
lets try to validate against 127.0.0.1
Co-authored-by: Daniel Ottiger <daniel.ottiger@ch.schindler.com>
SSL connection is performed in two steps:
First, a regular socket connection is established.
Then, SSL_connect/SSL_accept is called to establish SSL handshake.
If a network problem occurs during the second stage, SSL_connect on
the client may hang indefinitely.
The non-blocking mode solves this problem.
Co-authored-by: Michael Tseitlin <michael.tseitlin@concertio.com>
* *Add server fuzzer target and seed corpus
* Add fuzz_test option to Makefile
* Fix#685
* Try to fix Github actions on Ubuntu
* Added ReadTimeoutSSL test
* Comment out `-fsanitize=address`
* Rebase upstream changes
* remove address sanitizer temporarily
* Add separate Makefile for fuzzing
* 1. Remove special char from dictionary
2. Clean fuzzing/Makefile
* Use specific path to avoid accidently linking openssl version brought in by oss-fuzz
* remove addition of flags
* Refactor Makefile
* Add missing newline
* Add fuzztest to github workflow
* Fix
Co-authored-by: yhirose <yuji.hirose.bug@gmail.com>
* Backport std::make_unique from C++14.
* Replace shared_ptr with unique_ptr for better performance.
Co-authored-by: Ella <maxutong16@otcaix.iscas.ac.cn>
* Use move semantics instead of copy for functions
In some cases, a few more copies could be prevented by changing function definitions to accept parameters by const-ref, rather than by value, but I didn't want to change public signatures.
* Fix two use-after-move errors
* Add `cache_control` parameter to `set_mount_point`
Specifies the Cache-Control header value to return when specified. For example:
```
svr.set_mount_point("/assets", "public/assets", "public, max-age=604800, immutable");
```
* Add default for cache_control
Default to "no-cache", which is implicitly what is happening today.
* Change set_mount_point to accept Headers
* Don't use C++17 destructuring
* Fix memory leak due caused due to X509_STORE
* Add test for repro and address sanitizer to compiler flags
* Add comment
* Sync
* Associate ca_store with ssl context within set_ca_cert_store()
* Split SlowPost test
* Fix#674
Co-authored-by: yhirose <yuji.hirose.bug@gmail.com>
* Fix parsing to parse query string with single space char.
When passed ' ' as a query string, the server crashes cause of illegal memory access done in httplib::detail::split. Have added checks to make sure the split function has a valid string with length > 0.
* Fix parsing to parse query string with single space char.
* Fix server crash caused due to regex complexity while matching headers.
While parsing content-type header in multipart form request the server crashes due to the exhaustion of max iterations performed while matching the input string with content-type regex.
Have removed the regex which might use backtracking while matching and replaced it with manual string processing. Have added tests as well.
* Remove magic number
Co-authored-by: Ivan Fefer <fefer.ivan@gmail.com>
Co-authored-by: yhirose <yhirose@users.noreply.github.com>
Co-authored-by: Ivan Fefer <fefer.ivan@gmail.com>
* Fix parsing to parse query string with single space char.
When passed ' ' as a query string, the server crashes cause of illegal memory access done in httplib::detail::split. Have added checks to make sure the split function has a valid string with length > 0.
* Fix parsing to parse query string with single space char.
Correct the working directory of the execute_process call, to get the version from git tags.
The working directory should be the the directory of this libary. Otherwise, if you include httplib
as a git submodule and call add_subdirectory, the execute_process command will be run in a wrong
directory leading to error.
If you didn't have Git installed, execute_process never declared the
error variable, which led to it never parsing the header for a version.
So if Git wasn't installed, the version variable never got declared,
which caused errors.
This fixes that.
* Update httplib.h
When you disconnect and reconnect from the network, your network stack rewrites and updates /etc/resolv.conf accordingly. This configuration file is needed by the DNS resolver in the C library. The C library reads the DNS configuration from /etc/resolv.conf the first time, and caches it. It doesn't check, with every lookup, if the contents of /etc/resolv.conf have changed.
the solution is to add a call to res_init(), defined in resolv.h
* Update httplib.h
Had to create a custom FindBrotli package, as not all users have
PkgConfig installed (which Brotli uses). This file gets installed
alongside httplibConfig.cmake for the end-users convenience.
Set BROTLI_USE_STATIC_LIBS to ON if you want to find the static libs
instead of default shared.
Adds the HTTPLIB_REQUIRE_BROTLI (default off) and HTTPLIB_USE_BROTLI_IF_AVAILABLE
(default on) options, which work in the same manner as the other optional/required
dependency options.
Moved the scattered linking and definitions to a single call.
Updated some documentation about the new options.
Improved the in-tree support by setting the HTTPLIB_IS_USING_XYZ
variables in the main CMakeLists (as well as having them in the
httplibConfig.cmake file).
Fixes#582
Seems certain targets/hosts failed without these, as "_MSC_VER" is
undefined on MinGW, which caused the 'pragma comment(lib "libname")' to
fail.
Fixes#575
This gets us the full version (aka with the patch version), instead of
just major and minor version from user agent.
Falls back to the user agent if it fails.
It pulls the version from the user-agent string in the header, so it
will not need to be manually adjusted. This version file is installed so
that you can check for a specific version with find_package(httplib)
Also added HTTPLIB_INCLUDE_DIR (root path without header name), and
HTTPLIB_LIBRARY (only if compiled).
Added HTTPLIB_VERSION, and HTTPLIB_FOUND (although it's recommended
to check if the target exists).
Updated CMakeLists documentation for all this.
This option (default OFF) automatically splits the file (with split.py)
into a header & source file, then compiles it as a shared/static
library. This requires an installed Python v3 executable to work.
This also adds a HTTPLIB_IS_COMPILED boolean that's available after a
finfind_package(httplib) call.
Note that the minimum Cmake version increased to 3.12 because of FindPython3.
Hopefully this isn't a problem, as it's already 3 years old at this point.
* Revert "Removed CMakeLists.txt. (Fix#421)"
This reverts commit 8674555b88.
* Fail if cmake version too old
Previous behaviour is just a warning.
* Improve CMakeLists
Adds automatic dependency finding (if they were used).
Adds a way to require a specific version in the find_package(httplib) call.
You should link against the httplib::httplib IMPORTED target, which is
created automatically.
Add options to allow for strictly requiring OpenSSL/ZLIB
HTTPLIB_REQUIRE_OPENSSL & HTTPLIB_REQUIRE_ZLIB require the libs be found, or the build fails.
HTTPLIB_USE_OPENSSL_IF_AVAILABLE & HTTPLIB_USE_ZLIB_IF_AVAILABLE silently search for the libs.
If they aren't found, the build still continues, but shuts off support for those features.
* Add documentation to CMakeLists.txt
Has info on all the available options and what targets are produced.
Also put some things about installation on certain platforms.
In case we want to send a lot of data,
and the receiver is slower than the sender.
This will first fill up the receivers queues and after this
eventually also the senders queues,
until the socket is temporarily unable to accept more data to send.
select_write is done with an timeout of zero,
which makes the select call used always return immediately:
(see http://man7.org/linux/man-pages/man2/select.2.html)
This means that every marginal unavailability will make it return false
for is_writable and therefore httplib will immediately abort the transfer.
Therefore make this values configurable in the same way
as the read timeout already is.
Set the default write timeout to 5 seconds,
the same default value used for the read timeout.
According to RFC 3493 the socket option IPV6_V6ONLY
should be off by default, see
https://tools.ietf.org/html/rfc3493#page-22 (chapter 5.3).
However this does not seem to be the case on all systems.
For instance on any Windows OS, the option is on by default.
Therefore clear this option in order to allow
an server socket which can support IPv6 and IPv4 at the same time.
I use a custom TaskQueue, with variable number of workers, adding workers on demand is an easy task when new connection arrive (in enqueue function) however i need another funtion to be called even (or better) went no new connections arrives to reduce workers count. I only added a new virtual method in TaskQueue class to allow custom class to adjust workers size over time. Even if this methods is called frequenlty custom class can keep a "last_update" counter to check if need to adjust worker count or any other internal task. Without this function i need an external thread to make this adjust task.
* Fixed error:
ULONG_MAX is defined in the limits.h header file. Putting #include <climits>
```
httplib.h: In function ‘bool httplib::detail::read_content_chunked(httplib::Stream&, httplib::ContentReceiver)’:
httplib.h:1921:22: error: ‘ULONG_MAX’ was not declared in this scope
if (chunk_len == ULONG_MAX) { return false; }
^~~~~~~~~
httplib.h:1921:22: note: suggested alternative: ‘_SC_ULONG_MAX’
if (chunk_len == ULONG_MAX) { return false; }
^~~~~~~~~
_SC_ULONG_MAX
```
* Move #include <climits> to after #include <cassert>
We cannot trivially support such large chunks, and the maximum value
std::strtoul can parse accurately is ULONG_MAX-1. Error out early if the
length is longer than that.
detail::read_content_chunked was using std::stoul to parse the
hexadecimal chunk lengths for "Transfer-Encoding: chunked" requests.
This throws an exception if the string does not begin with any valid
digits. read_content_chunked is not called in the context of a try block
so this caused the process to terminate.
Rather than use exceptions, I opted for std::stroul, which is similar to
std::stoul but does not throw exceptions. Since malformed user input is
not particularly exceptional, and some projects are compiled without
exception support, this approach seems both more portable and more
correct.
* SSLServer: add constructor to pass ssl-certificates and key from memory
* SSLClient: add constructor to pass ssl-certificates and key from memory
* add TestCase for passing certificates from memory to SSLClient/SSLServer
Previously, calling set_content always resulted in 's' being copied. With this change, there will still be the same number of copies made (1) when doing `set_content(my_value, ...)`, but there will be no copies if a caller elects to do `set_content(std::move(value), ...)` or `set_content(some_function_that_returns_a_temporary(), ...)` instead.
The regex that parses header lines potentially causes an unlimited
amount of backtracking, which can cause an exception in the libc++ regex
engine.
The exception that occurs looks like this and is identical to the
message of the exception fixed in
https://github.com/yhirose/cpp-httplib/pull/280:
libc++abi.dylib: terminating with uncaught exception of type
std::__1::regex_error: The complexity of an attempted match
against a regular expression exceeded a pre-set level.
This commit eliminates the problematic backtracking.
Since the WSA_FLAG_NO_HANDLE_INHERIT is only supported on Windows 7 SP1 and above the socket creation fails on older Windows Systems.
Let's try to create a socket the old way in this case.
Reference:
https://docs.microsoft.com/en-us/windows/win32/api/winsock2/nf-winsock2-wsasocketa
WSA_FLAG_NO_HANDLE_INHERIT:
This flag is supported on Windows 7 with SP1, Windows Server 2008 R2 with SP1, and later
libc++ (the implementation of the C++ standard library usually used by
Clang) throws an exception for the regex used by parse_headers before
this patch for certain strings. Work around this by simplifying the
regex and parsing the header lines "by hand" partially. I have repro'd
this problem with Xcode 11.1 which I believe uses libc++ version 8.
This may be a bug in libc++ as I can't see why the regex would result in
asymptotic run-time complexity for any strings. However, it may take a
while for libc++ to be fixed and for everyone to migrate to it, so it
makes sense to work around it in this codebase for now.
HTTP Whitespace and regex whitespace are not the same, so we can't use
\s in regexes when parsing HTTP headers. Instead, explicitly specify
what is considered whitespace in the regex.
- This compliments the existing `bind_to_any_port()`
where you can determine if the bind succeeded prior
to calling `listen_after_bind()` but allows you to
specify the port.
While trying to implement streaming of internet radio, where a ContentReceiver is needed to handle the audio data, I had the problem, that important information about the stream data is part of the HTTP header (e.g. size of audio chunks between meta data), so I added a ResponseHandler and a new Get variant, to gain access to the header before handling the first chunk of data.
The ResponseHandler can abort the request by returning false, in the same way as the ContentReceiver.
A test case was also added.
for /f "usebackq tokens=*" %%i in (`"%ProgramFiles(x86)%\Microsoft Visual Studio\Installer\vswhere.exe" -latest -property installationPath`) do set VSDIR=%%i
call "%VSDIR%\VC\Auxiliary\Build\vcvarsall.bat" x86 || exit /b 1
cd test && make test_split EXTRA_CXXFLAGS="-fno-exceptions -DCPPHTTPLIB_NO_EXCEPTIONS" && make test_openssl_parallel EXTRA_CXXFLAGS="-fno-exceptions -DCPPHTTPLIB_NO_EXCEPTIONS"
This document describes the streaming extensions for cpp-httplib, providing an iterator-style API for handling HTTP responses incrementally with **true socket-level streaming**.
> **Important Notes**:
>
> - **No Keep-Alive**: Each `stream::Get()` call uses a dedicated connection that is closed after the response is fully read. For connection reuse, use `Client::Get()`.
> - **Single iteration only**: The `next()` method can only iterate through the body once.
> - **Result is not thread-safe**: While `stream::Get()` can be called from multiple threads simultaneously, the returned `stream::Result` must be used from a single thread only.
## Overview
The streaming API allows you to process HTTP response bodies chunk by chunk using an iterator-style pattern. Data is read directly from the network socket, enabling low-memory processing of large responses. This is particularly useful for:
| SSE with auto-reconnect | `SSEClient` (see [README-sse.md](README-sse.md)) |
| LLM streaming (JSON Lines) | `stream::Get()` |
| Large file download | `stream::Get()` or `open_stream()` |
| Reverse proxy | `open_stream()` |
| Small responses with Keep-Alive | `Client::Get()` |
## API Reference
### Low-Level API: `StreamHandle`
The `StreamHandle` struct provides direct control over streaming responses. It takes ownership of the socket connection and reads data directly from the network.
> **Note:** When using `open_stream()`, the connection is dedicated to streaming and **Keep-Alive is not supported**. For Keep-Alive connections, use `client.Get()` instead.
A simple, blocking WebSocket implementation for C++11.
> [!IMPORTANT]
> This is a blocking I/O WebSocket implementation using a thread-per-connection model (plus one heartbeat thread per connection). It is intended for small- to mid-scale workloads; handling large numbers of simultaneous WebSocket connections is outside the design target of this library. If you need high-concurrency WebSocket support with non-blocking/async I/O (e.g., thousands of simultaneous connections), this is not the one that you want.
> [!NOTE]
> WebSocket extensions (`permessage-deflate` and others defined by RFC 6455) are **not supported**. If a client proposes an extension via `Sec-WebSocket-Extensions`, the server silently declines it — the negotiated connection always runs without extensions.
## Features
- **RFC 6455 compliant**: Full WebSocket protocol support (extensions are not implemented)
- **Server and Client**: Both sides included
- **SSL/TLS support**: `wss://` scheme for secure connections
- **Text and Binary**: Both message types supported
Returned by `read()`. Since `Fail` is `0`, the result works naturally in boolean contexts — `while (ws.read(msg))` continues until the connection closes. When you need to distinguish text from binary, check the return value directly.
The `SubProtocolSelector` receives the list of subprotocols proposed by the client (from the `Sec-WebSocket-Protocol` header) and returns the selected one. Return an empty string to decline all proposed subprotocols.
### WebSocket (Server-side)
Passed to the handler registered with `Server::WebSocket()`. The handler runs in a dedicated thread per connection.
```cpp
// Read next message (blocks until received, returns Fail/Text/Binary)
The server can negotiate a subprotocol with the client using `Sec-WebSocket-Protocol`. This is required for protocols like GraphQL over WebSocket (`graphql-ws`) and MQTT.
```cpp
// Server: register a handler with a subprotocol selector
By default the heartbeat only sends pings — it does not enforce that pongs come back. To detect a silently dropped connection faster, enable the max-missed-pongs check. Once `max_missed_pongs` consecutive pings go unanswered, the heartbeat thread closes the connection with `CloseStatus::GoingAway` and the reason `"pong timeout"`.
```cpp
ws.set_websocket_max_missed_pongs(2);// close after 2 consecutive unacked pings
```
The server side has the same `set_websocket_max_missed_pongs()`.
With the default ping interval of 30 seconds, `max_missed_pongs = 2` detects a dead peer within ~60 seconds. The counter is reset every time a Pong frame is received, so the mechanism only works when your code is actively calling `read()` — exactly the pattern a normal WebSocket client already uses.
**The default is `0`**, which means "never close the connection because of missing pongs." Pings are still sent on the heartbeat interval, but their responses are not checked. Even so, a dead connection does not linger forever: while your code is inside `read()`, `CPPHTTPLIB_WEBSOCKET_READ_TIMEOUT_SECOND` (default **300 seconds = 5 minutes**) acts as a backstop and `read()` fails if no frame arrives in time. `max_missed_pongs` is the knob for detecting an unresponsive peer faster than that 5-minute fallback.
## Threading Model
WebSocket connections share the same thread pool as HTTP requests. Each WebSocket connection occupies one thread for its entire lifetime.
The default thread pool uses dynamic scaling: it maintains a base thread count of `CPPHTTPLIB_THREAD_POOL_COUNT` (8 or `std::thread::hardware_concurrency() - 1`, whichever is greater) and can scale up to 4x that count under load (`CPPHTTPLIB_THREAD_POOL_MAX_COUNT`). When all base threads are busy, temporary threads are spawned automatically up to the maximum. These dynamic threads exit after an idle timeout (`CPPHTTPLIB_THREAD_POOL_IDLE_TIMEOUT`, default 3 seconds).
This dynamic scaling helps accommodate WebSocket connections alongside HTTP requests. However, if you expect many simultaneous WebSocket connections, you should configure the thread pool accordingly:
title: "C01. Get the Response Body / Save to a File"
order: 1
status: "draft"
---
## Get it as a string
```cpp
httplib::Clientcli("http://localhost:8080");
autores=cli.Get("/hello");
if(res&&res->status==200){
std::cout<<res->body<<std::endl;
}
```
`res->body` is a `std::string`, ready to use as-is. The entire response is loaded into memory.
> **Warning:** If you fetch a large file with `res->body`, it all goes into memory. For large downloads, use a `ContentReceiver` as shown below.
## Save to a file
```cpp
httplib::Clientcli("http://localhost:8080");
std::ofstreamofs("output.bin",std::ios::binary);
if(!ofs){
std::cerr<<"Failed to open file"<<std::endl;
return1;
}
autores=cli.Get("/large-file",
[&](constchar*data,size_tlen){
ofs.write(data,len);
returnstatic_cast<bool>(ofs);
});
```
With a `ContentReceiver`, data arrives in chunks. You can write each chunk straight to disk without buffering the whole body in memory — perfect for large file downloads.
Return `false` from the callback to abort the download. In the example above, if writing to `ofs` fails, the download stops automatically.
> **Detail:** Want to check response headers like Content-Length before downloading? Combine a `ResponseHandler` with a `ContentReceiver`.
>
> ```cpp
> auto res = cli.Get("/large-file",
> [](const httplib::Response &res) {
> auto len = res.get_header_value("Content-Length");
> std::cout << "Size: " << len << std::endl;
> return true; // return false to skip the download
> },
> [&](const char *data, size_t len) {
> ofs.write(data, len);
> return static_cast<bool>(ofs);
> });
> ```
>
> The `ResponseHandler` is called after headers arrive but before the body. Return `false` to skip the download entirely.
> To show download progress, see [C11. Use the progress callback](c11-progress-callback).
cpp-httplib doesn't include a JSON parser. Use a library like [nlohmann/json](https://github.com/nlohmann/json) to build and parse JSON. The examples here use `nlohmann/json`.
Pass the JSON string as the second argument to `Post()` and the Content-Type as the third. The same pattern works with `Put()` and `Patch()`.
> **Warning:** If you omit the Content-Type (the third argument), the server may not recognize the body as JSON. Always specify `"application/json"`.
## Receive a JSON response
```cpp
autores=cli.Get("/api/users/1");
if(res&&res->status==200){
autoj=nlohmann::json::parse(res->body);
std::cout<<j["name"]<<std::endl;
}
```
`res->body` is a `std::string`, so you can pass it straight to your JSON library.
> **Note:** Servers sometimes return HTML on errors. Check the status code before parsing to be safe. Some APIs also require an `Accept: application/json` header. If you're calling a JSON API repeatedly, [C03. Set default headers](c03-default-headers) can save you some boilerplate.
> For how to receive and return JSON on the server side, see [S02. Receive JSON requests and return JSON responses](s02-json-api).
When you want the same headers on every request, use `set_default_headers()`. Once set, they're attached automatically to every request sent from that client.
## Basic usage
```cpp
httplib::Clientcli("https://api.example.com");
cli.set_default_headers({
{"Accept","application/json"},
{"User-Agent","my-app/1.0"},
});
autores=cli.Get("/users");
```
Register the headers you need on every API call — like `Accept` or `User-Agent` — in one place. No need to repeat them on each request.
## Send a Bearer token on every request
```cpp
httplib::Clientcli("https://api.example.com");
cli.set_default_headers({
{"Authorization","Bearer "+token},
{"Accept","application/json"},
});
autores1=cli.Get("/me");
autores2=cli.Get("/projects");
```
Set the auth token once, and every subsequent request carries it. Handy when you're writing an API client that hits multiple endpoints.
> **Note:** `set_default_headers()` **replaces** the existing default headers. Even if you only want to add one, pass the full set again.
## Combine with per-request headers
You can still pass extra headers on individual requests, even with defaults set.
```cpp
httplib::Headersheaders={
{"X-Request-ID","abc-123"},
};
autores=cli.Get("/users",headers);
```
Per-request headers are **added** on top of the defaults. Both are sent to the server.
> For details on Bearer token auth, see [C06. Call an API with a Bearer token](c06-bearer-token).
By default, cpp-httplib does not follow HTTP redirects (3xx). If the server returns `302 Found`, you'll get it as a response with status code 302 — nothing more.
To follow redirects automatically, call `set_follow_location(true)`.
## Follow redirects
```cpp
httplib::Clientcli("http://example.com");
cli.set_follow_location(true);
autores=cli.Get("/old-path");
if(res&&res->status==200){
std::cout<<res->body<<std::endl;
}
```
With `set_follow_location(true)`, the client reads the `Location` header and reissues the request to the new URL automatically. The final response ends up in `res`.
## Redirects from HTTP to HTTPS
```cpp
httplib::Clientcli("http://example.com");
cli.set_follow_location(true);
autores=cli.Get("/");
```
Many sites redirect HTTP traffic to HTTPS. With `set_follow_location(true)` on, this case is handled transparently — the client follows redirects even when the scheme or host changes.
> **Warning:** To follow redirects to HTTPS, you need to build cpp-httplib with OpenSSL (or another TLS backend). Without TLS support, redirects to HTTPS will fail.
> **Note:** Following redirects adds to the total request time. See [C12. Set timeouts](c12-timeouts) for timeout configuration.
For endpoints that require Basic authentication, pass the username and password to `set_basic_auth()`. cpp-httplib builds the `Authorization: Basic ...` header for you.
## Basic usage
```cpp
httplib::Clientcli("https://api.example.com");
cli.set_basic_auth("alice","s3cret");
autores=cli.Get("/private");
if(res&&res->status==200){
std::cout<<res->body<<std::endl;
}
```
Set it once, and every request from that client carries the credentials. No need to build the header each time.
## Per-request usage
If you want credentials on only one specific request, pass headers directly.
`make_basic_authentication_header()` builds the Base64-encoded header for you.
> **Warning:** Basic authentication **encodes** credentials in Base64 — it does not encrypt them. Always use it over HTTPS. Over plain HTTP, your password travels the network in the clear.
## Digest authentication
For the more secure Digest authentication scheme, use `set_digest_auth()`. This is only available when cpp-httplib is built with OpenSSL (or another TLS backend).
```cpp
cli.set_digest_auth("alice","s3cret");
```
> To call an API with a Bearer token, see [C06. Call an API with a Bearer token](c06-bearer-token).
For Bearer token authentication — common in OAuth 2.0 and modern Web APIs — use `set_bearer_token_auth()`. Pass the token and cpp-httplib builds the `Authorization: Bearer <token>` header for you.
Set it once and every subsequent request carries the token. This is the go-to pattern for token-based APIs like GitHub, Slack, or your own OAuth service.
## Per-request usage
When you want the token on only one request — or need a different token per request — pass it via headers.
title: "C07. Upload a File as Multipart Form Data"
order: 7
status: "draft"
---
When you want to send a file the same way an HTML `<input type="file">` does, use multipart form data (`multipart/form-data`). cpp-httplib offers two APIs — `UploadFormDataItems` and `FormDataProviderItems` — and you pick between them based on **file size**.
## Send a small file
Read the file into memory first, then send it. For small files, this is the simplest path.
Each `UploadFormData` entry is `{name, content, filename, content_type}`. For plain text fields, leave `filename` and `content_type` empty.
## Stream a large file
To avoid loading the whole file into memory, use `make_file_provider()`. It reads the file in chunks as it sends — so even huge files won't blow up your memory footprint.
The arguments to `make_file_provider()` are `(form name, file path, file name, content type)`. Leave the file name empty to use the file path as-is.
> **Note:** You can mix `UploadFormDataItems` and `FormDataProviderItems` in the same request. A clean split is: text fields in `UploadFormDataItems`, files in `FormDataProviderItems`.
> To show upload progress, see [C11. Use the progress callback](c11-progress-callback).
Sometimes you want to send a file's contents as the request body directly — no multipart wrapping. This is common for S3-compatible APIs or endpoints that take raw image data. For this, use `make_file_body()`.
`make_file_body()` returns a pair of file size and a `ContentProvider`. Pass them to `Post()` or `Put()` and the file contents flow straight into the request body.
The `ContentProvider` reads the file in chunks, so even huge files never sit fully in memory.
## When the file can't be opened
If the file can't be opened, `make_file_body()` returns `size` as `0` and `provider` as an empty function object. Sending that would produce garbage — always check `size` first.
> **Warning:** `make_file_body()` needs to fix the Content-Length up front, so it reads the file size ahead of time. If the file size might change mid-upload, this API isn't the right fit.
> To send the file as multipart form data instead, see [C07. Upload a file as multipart form data](c07-multipart-upload).
When you don't know the body size up front — for data generated on the fly or piped from another stream — use `ContentProviderWithoutLength`. The client sends the body with HTTP chunked transfer encoding.
## Basic usage
```cpp
httplib::Clientcli("http://localhost:8080");
autores=cli.Post("/stream",
[&](size_toffset,httplib::DataSink&sink){
std::stringchunk=produce_next_chunk();
if(chunk.empty()){
sink.done();// done sending
returntrue;
}
returnsink.write(chunk.data(),chunk.size());
},
"application/octet-stream");
```
The lambda's job is just: produce the next chunk and send it with `sink.write()`. When there's no more data, call `sink.done()` and you're finished.
## When the size is known
If you **do** know the total size ahead of time, use the `ContentProvider` overload (taking `size_t offset, size_t length, DataSink &sink`) and pass the total size as well.
With a known size, the request carries a Content-Length header — so the server can show progress. Prefer this form when you can.
> **Detail:** `sink.write()` returns a `bool` indicating whether the write succeeded. If it returns `false`, the connection is gone — return `false` from the lambda to stop.
> If you're just sending a file, `make_file_body()` is easier. See [C08. POST a file as raw binary](c08-post-file-body).
To receive a response body chunk by chunk, use a `ContentReceiver`. It's the obvious choice for large files, but it's equally handy for NDJSON (newline-delimited JSON) or log streams where you want to start processing data as it arrives.
## Process each chunk
```cpp
httplib::Clientcli("http://localhost:8080");
autores=cli.Get("/logs/stream",
[](constchar*data,size_tlen){
std::cout.write(data,len);
std::cout.flush();
returntrue;// return false to stop receiving
});
```
Data arrives in the lambda in the order it's received from the server. Return `false` from the callback to stop the download partway through.
## Parse NDJSON line by line
Here's a buffered approach for processing newline-delimited JSON one line at a time.
Accumulate into a buffer, then pull out and parse one line each time you see a newline. This is the standard pattern for consuming a streaming API in real time.
> **Warning:** When you pass a `ContentReceiver`, `res->body` stays **empty**. Store or process the body inside the callback yourself.
> To track download progress, combine this with [C11. Use the progress callback](c11-progress-callback).
> For Server-Sent Events (SSE), see [E04. Receive SSE on the client](e04-sse-client).
To display download or upload progress, pass a `DownloadProgress` or `UploadProgress` callback. Both take two arguments: `(current, total)`.
## Download progress
```cpp
httplib::Clientcli("http://localhost:8080");
autores=cli.Get("/large-file",
[](size_tcurrent,size_ttotal){
autopercent=(total>0)?(current*100/total):0;
std::cout<<"\rDownloading: "<<percent<<"% ("
<<current<<"/"<<total<<")"<<std::flush;
returntrue;// return false to abort
});
std::cout<<std::endl;
```
The callback fires each time data arrives. `total` comes from the Content-Length header — if the server doesn't send one, it may be `0`. In that case, you can't compute a percentage, so just display bytes received.
## Upload progress
Uploads work the same way. Pass an `UploadProgress` as the last argument to `Post()` or `Put()`.
Return `false` from the callback to abort the transfer. This is how you wire up a "Cancel" button in a UI — flip a flag, and the next progress tick stops the transfer.
```cpp
std::atomic<bool>cancelled{false};
autores=cli.Get("/large-file",
[&](size_tcurrent,size_ttotal){
return!cancelled.load();
});
```
> **Note:** `ContentReceiver` and the progress callback can be used together. When you want to stream to a file and show progress at the same time, pass both.
> For a concrete example of saving to a file, see [C01. Get the response body / save to a file](c01-get-response-body).
The client has three kinds of timeouts, each set independently.
| Kind | API | Default | Meaning |
| --- | --- | --- | --- |
| Connection | `set_connection_timeout` | 300s | Time to wait for the TCP connection to establish |
| Read | `set_read_timeout` | 300s | Time to wait for a single `recv` when receiving the response |
| Write | `set_write_timeout` | 5s | Time to wait for a single `send` when sending the request |
## Basic usage
```cpp
httplib::Clientcli("http://localhost:8080");
cli.set_connection_timeout(5,0);// 5 seconds
cli.set_read_timeout(10,0);// 10 seconds
cli.set_write_timeout(10,0);// 10 seconds
autores=cli.Get("/api/data");
```
Pass seconds and microseconds as two arguments. If you don't need the sub-second part, you can omit the second argument.
## Use `std::chrono`
There's also an overload that takes a `std::chrono` duration directly. It's easier to read — recommended.
```cpp
usingnamespacestd::chrono_literals;
cli.set_connection_timeout(5s);
cli.set_read_timeout(10s);
cli.set_write_timeout(500ms);
```
## Watch out for the long 300s default
Connection and read timeouts default to **300 seconds (5 minutes)**. If the server hangs, you'll be waiting five minutes by default. Shorter values are usually a better idea.
```cpp
cli.set_connection_timeout(3s);
cli.set_read_timeout(10s);
```
> **Warning:** The read timeout covers a single receive call — not the whole request. If data keeps trickling in during a large download, the request can take half an hour without ever hitting the timeout. To cap the total request time, use [C13. Set an overall timeout](c13-max-timeout).
The three timeouts from [C12. Set timeouts](c12-timeouts) all apply to a single `send` or `recv` call. To cap the total time a request can take, use `set_max_timeout()`.
## Basic usage
```cpp
httplib::Clientcli("http://localhost:8080");
cli.set_max_timeout(5000);// 5 seconds (in milliseconds)
autores=cli.Get("/slow-endpoint");
```
The value is in milliseconds. Connection, send, and receive together — the whole request is aborted if it exceeds the limit.
## Use `std::chrono`
There's also an overload that takes a `std::chrono` duration.
```cpp
usingnamespacestd::chrono_literals;
cli.set_max_timeout(5s);
```
## When to use which
`set_read_timeout` fires when no data arrives for a while. If data keeps trickling in bit by bit, it will never fire. An endpoint that sends one byte per second can make `set_read_timeout` useless no matter how short you set it.
`set_max_timeout` caps elapsed time, so it handles those cases cleanly. It's great for calls to external APIs or anywhere you don't want users waiting forever.
```cpp
cli.set_connection_timeout(3s);
cli.set_read_timeout(10s);
cli.set_max_timeout(30s);// abort if the whole request takes over 30s
```
> **Note:** `set_max_timeout()` works alongside the regular timeouts. Short stalls get caught by `set_read_timeout`; long-running requests get capped by `set_max_timeout`. Use both for a safety net.
title: "C14. Understand Connection Reuse and Keep-Alive"
order: 14
status: "draft"
---
When you send multiple requests through the same `httplib::Client` instance, the TCP connection is reused automatically. HTTP/1.1 Keep-Alive does the work for you — you don't pay the TCP and TLS handshake cost on every call.
## Connections are reused automatically
```cpp
httplib::Clientcli("https://api.example.com");
autores1=cli.Get("/users/1");
autores2=cli.Get("/users/2");// reuses the same connection
autores3=cli.Get("/users/3");// reuses the same connection
```
No special config required. Just hold on to `cli` — internally, the socket stays open across calls. The effect is especially noticeable over HTTPS, where the TLS handshake is expensive.
## Disable Keep-Alive explicitly
To force a fresh connection every time, call `set_keep_alive(false)`. Mostly useful for testing.
```cpp
cli.set_keep_alive(false);
```
For normal use, leave it on (the default).
## Don't create a `Client` per request
If you create a `Client` inside a loop and let it fall out of scope each iteration, you lose the reuse benefit. Create the instance outside the loop.
```cpp
// Bad: a new connection every iteration
for(autoid:ids){
httplib::Clientcli("https://api.example.com");
cli.Get("/users/"+id);
}
// Good: the connection is reused
httplib::Clientcli("https://api.example.com");
for(autoid:ids){
cli.Get("/users/"+id);
}
```
## Concurrent requests
If you want to send requests in parallel from multiple threads, give each thread its own `Client` instance. A single `Client` uses a single TCP connection, so firing concurrent requests at the same instance ends up serializing them anyway.
> **Note:** If the server closes the connection after its Keep-Alive timeout, cpp-httplib reconnects and retries transparently. You don't need to handle this in application code.
With `set_compress(true)`, the body of POST or PUT requests gets gzipped before sending. The server needs to handle compressed bodies too.
## Decompress the response
```cpp
httplib::Clientcli("https://api.example.com");
cli.set_decompress(true);// on by default
autores=cli.Get("/api/data");
std::cout<<res->body<<std::endl;
```
With `set_decompress(true)`, the client automatically decompresses responses that arrive with `Content-Encoding: gzip` or similar. `res->body` contains the decompressed data.
It's on by default, so normally you don't need to do anything. Set it to `false` only if you want the raw compressed bytes.
> **Warning:** If you build without `CPPHTTPLIB_ZLIB_SUPPORT`, calling `set_compress()` or `set_decompress()` does nothing. If compression isn't working, check the macro definition first.
To route traffic through a corporate network or a specific path, send requests via an HTTP proxy. Just pass the proxy host and port to `set_proxy()`.
## Basic usage
```cpp
httplib::Clientcli("https://api.example.com");
cli.set_proxy("proxy.internal",8080);
autores=cli.Get("/users");
```
The request goes through the proxy. For HTTPS, the client uses the CONNECT method to tunnel through — no extra setup required.
## Proxy authentication
If the proxy itself requires authentication, use `set_proxy_basic_auth()` or `set_proxy_bearer_token_auth()`.
```cpp
cli.set_proxy("proxy.internal",8080);
cli.set_proxy_basic_auth("user","password");
```
```cpp
cli.set_proxy_bearer_token_auth("token");
```
If cpp-httplib is built with OpenSSL (or another TLS backend), you can also use Digest authentication for the proxy.
```cpp
cli.set_proxy_digest_auth("user","password");
```
## Combine with end-server authentication
Proxy authentication is separate from authenticating to the end server ([C05. Use Basic authentication](c05-basic-auth), [C06. Call an API with a Bearer token](c06-bearer-token)). When both are needed, set both.
- a hostname suffix (e.g. `example.com`) — matches `example.com` itself and any subdomain (`foo.example.com`). A leading dot is permitted but informational; both forms are equivalent.
- a single IP literal (e.g. `192.168.1.1`, `::1`)
- a CIDR block (e.g. `10.0.0.0/8`, `fe80::/10`)
Hostname matching is case-insensitive and uses a dot-boundary rule, so an entry of `example.com` does **not** match `evilexample.com`. IP comparisons are normalized through `inet_pton`, so `127.0.0.1` cannot be bypassed via alternate string forms (e.g. `127.000.000.001`). When an entry matches, the `Proxy-Authorization` header is suppressed as well.
Malformed entries are silently dropped. Port-specific entries such as `example.com:8080` are not supported (cpp-httplib's other host-keyed APIs are also keyed on hostname only).
## Read proxy settings from the environment
cpp-httplib doesn't touch `HTTP_PROXY` / `HTTPS_PROXY` / `NO_PROXY` on its own — the config API is always explicit, the same way `set_ca_cert_path()` is. If you'd like that behavior, read the variables in your application and feed them to `set_proxy()` and `set_no_proxy()`.
```cpp
if(constchar*v=std::getenv("no_proxy")){
std::vector<std::string>patterns;
std::stringstreamss(v);
for(std::stringitem;std::getline(ss,item,',');){
if(!item.empty()){patterns.push_back(item);}
}
cli.set_no_proxy(patterns);
}
```
If you also read `HTTP_PROXY` yourself, honor the lowercase `http_proxy` only. The uppercase form is poisoned in CGI/FastCGI environments by the `Proxy:` request header ([CVE-2016-5385 / "httpoxy"](https://httpoxy.org/)). `HTTPS_PROXY` and `NO_PROXY` are safe in either case because their names don't begin with `HTTP_`.
`cli.Get()`, `cli.Post()`, and friends return a `Result`. When the request fails — can't reach the server, times out, etc. — the result is "falsy". To get the specific reason, use `Result::error()`.
Use `if (res)` to check success. On failure, `res.error()` returns a `httplib::Error` enum value. Pass it to `to_string()` to get a human-readable description.
## Common errors
| Value | Meaning |
| --- | --- |
| `Error::Connection` | Couldn't connect to the server |
When an HTTPS request fails, `res.error()` returns values like `Error::SSLConnection` or `Error::SSLServerVerification`. Sometimes that's not enough to pinpoint the cause. That's where `Result::ssl_error()` and `Result::ssl_backend_error()` help.
`ssl_error()` returns the error code from the SSL library (e.g., OpenSSL's `SSL_get_error()`). `ssl_backend_error()` gives you the backend's more detailed error value — for OpenSSL, that's `ERR_get_error()`.
## Format OpenSSL errors as strings
When you have a value from `ssl_backend_error()`, pass it to OpenSSL's `ERR_error_string()` to get a readable message.
The callback you pass to `set_logger()` fires once for each completed request. You get both the request and the response as arguments — so you can log the method, path, status, headers, body, or whatever else you need.
## Catch errors only
When a network-layer error happens (like `Error::Connection`), `set_logger()` is **not** called — there's no response to log. For those cases, use `set_error_logger()`.
> **Note:** The log callbacks run synchronously on the same thread as the request. Heavy work inside them slows the request down — push it to a background queue if you need to do anything expensive.
Server-Sent Events (SSE) is a simple protocol for pushing events one-way from server to client. The connection stays open, and the server can send data whenever it wants. It's lighter than WebSocket and fits entirely within HTTP — a nice combination.
cpp-httplib doesn't have a dedicated SSE server API, but you can implement one with `set_chunked_content_provider()` and `text/event-stream`.
When the client disconnects, call `sink.done()` to stop. Details in [S16. Detect client disconnection](s16-disconnect).
## Heartbeats via comment lines
Lines starting with `:` are SSE comments — clients ignore them, but they **keep the connection alive**. Handy for preventing proxies and load balancers from closing idle connections.
```cpp
// heartbeat every 30 seconds
if(tick_count%30==0){
std::stringping=": ping\n\n";
sink.write(ping.data(),ping.size());
}
```
## Relationship with the thread pool
SSE connections stay open, so each client holds a worker thread. For lots of concurrent connections, enable dynamic scaling on the thread pool.
```cpp
svr.new_task_queue=[]{
returnnewhttplib::ThreadPool(8,128);
};
```
See [S21. Configure the thread pool](s21-thread-pool).
> **Note:** When `data:` contains newlines, split it into multiple `data:` lines — one per line. This is how the SSE spec requires multiline data to be transmitted.
> For event names, see [E02. Use named events in SSE](e02-sse-event-names). For the client side, see [E04. Receive SSE on the client](e04-sse-client).
SSE lets you send multiple kinds of events over the same stream. Give each one a name with the `event:` field, and the client can dispatch to a different handler per type. Great for things like "new message", "user joined", "user left" in a chat app.
A message is `event:` → `data:` → blank line. If you omit `event:`, the client treats it as a default `"message"` event.
## Attach IDs for reconnect
When you include an `id:` field, the client automatically sends it back as `Last-Event-ID` on reconnect, telling the server "here's how far I got."
```cpp
autosend_event=[](httplib::DataSink&sink,
conststd::string&event,
conststd::string&data,
conststd::string&id){
std::stringmsg="id: "+id+"\n"
+"event: "+event+"\n"
+"data: "+data+"\n\n";
sink.write(msg.data(),msg.size());
};
send_event(sink,"message","Hello!","42");
```
The ID format is up to you. Monotonic counters or UUIDs both work — just pick something unique and orderable on the server side. See [E03. Handle SSE reconnection](e03-sse-reconnect) for details.
## JSON payloads in data
For structured data, the usual move is to put JSON in `data:`.
```cpp
nlohmann::jsonpayload={
{"user","alice"},
{"text","Hello!"},
};
send_event(sink,"message",payload.dump(),"42");
```
On the client, parse the incoming `data` as JSON to get the original object back.
## Data with newlines
If the data value contains newlines, split it across multiple `data:` lines.
```cpp
std::stringmsg="data: line1\n"
"data: line2\n"
"data: line3\n\n";
sink.write(msg.data(),msg.size());
```
On the client side, these come back as a single `data` string with newlines.
> **Note:** Using `event:` makes client-side dispatch cleaner, but it also helps in the browser DevTools — events are easier to filter by type. That matters more than you'd expect while debugging.
SSE connections drop for all sorts of network reasons. Clients automatically try to reconnect, so it's a good idea to make your server resume from where it left off.
## Read `Last-Event-ID`
When the client reconnects, it sends the ID of the last event it received in the `Last-Event-ID` header. The server reads that and picks up from the next one.
On the first connect, `Last-Event-ID` is empty, so start from `0`. On reconnect, resume from the next ID. Event history is the server's responsibility — you need to keep recent events around somewhere.
## Set the reconnect interval
Sending a `retry:` field tells the client how long to wait before reconnecting, in milliseconds.
```cpp
std::stringmsg="retry: 5000\n\n";// reconnect after 5 seconds
sink.write(msg.data(),msg.size());
```
Usually you send this once at the start. During peak load or maintenance windows, a longer retry interval helps reduce reconnect storms.
## Buffer recent events
To support reconnection, keep a rolling buffer of recent events on the server.
When a client reconnects, call `since(last_id)` to send any events it missed.
## How much to keep
The buffer size is a tradeoff between memory and how far back a client can resume. It depends on the use case:
- Real-time chat: a few minutes to half an hour
- Notifications: the last N items
- Trading data: persist to a database and pull from there
> **Warning:** `Last-Event-ID` is a client-provided value — don't trust it blindly. If you read it as a number, validate the range. If it's a string, sanitize it.
cpp-httplib ships a dedicated `sse::SSEClient` class. It handles auto-reconnect, per-event-name dispatch, and `Last-Event-ID` tracking for you — so receiving SSE is painless.
Build an `SSEClient` with a `Client` and a path, register a callback with `on_message()`, and call `start()`. The event loop kicks in and automatically reconnects if the connection drops.
## Dispatch by event name
When the server sends events with an `event:` field, register a handler per name via `on_event()`.
```cpp
sse.on_event("message",[](constauto&msg){
std::cout<<"chat: "<<msg.data<<std::endl;
});
sse.on_event("join",[](constauto&msg){
std::cout<<msg.data<<" joined"<<std::endl;
});
sse.on_event("leave",[](constauto&msg){
std::cout<<msg.data<<" left"<<std::endl;
});
```
`on_message()` serves as a generic fallback for unnamed events (the default `message` type).
Hook into connection open and error events. Even when the error handler fires, `SSEClient` keeps trying to reconnect in the background.
## Run asynchronously
If you don't want to block the main thread, use `start_async()`.
```cpp
sse.start_async();
// main thread continues to do other things
do_other_work();
// when you're done, stop it
sse.stop();
```
`start_async()` spawns a background thread to run the event loop. Use `stop()` to shut it down cleanly.
## Configure reconnection
You can tune the reconnect interval and maximum retries.
```cpp
sse.set_reconnect_interval(5000);// 5 seconds
sse.set_max_reconnect_attempts(10);// up to 10 (0 = unlimited)
```
If the server sends a `retry:` field, that takes precedence.
## Automatic Last-Event-ID
`SSEClient` tracks the `id` of each received event internally and sends it back as `Last-Event-ID` on reconnect. As long as the server sends events with `id:`, this all works automatically.
> **Note:** `SSEClient::start()` blocks, which is fine for a one-off command-line tool. For GUI apps or embedded in a server, the `start_async()` + `stop()` pair is the usual pattern.
> For the server side, see [E01. Implement an SSE server](e01-sse-server).
A collection of recipes that answer "How do I...?" questions. Each recipe is self-contained — read only what you need. For an introduction to the basics, see the [Tour](../tour/).
## Client
### Basics
- [C01. Get the response body / save to a file](c01-get-response-body)
- [C02. Send and receive JSON](c02-json)
- [C03. Set default headers](c03-default-headers)
- [C04. Follow redirects](c04-follow-location)
### Authentication
- [C05. Use Basic authentication](c05-basic-auth)
- [C06. Call an API with a Bearer token](c06-bearer-token)
### File Upload
- [C07. Upload a file as multipart form data](c07-multipart-upload)
- [C08. POST a file as raw binary](c08-post-file-body)
- [C09. Send the body with chunked transfer](c09-chunked-upload)
### Streaming & Progress
- [C10. Receive a response as a stream](c10-stream-response)
- [C11. Use the progress callback](c11-progress-callback)
### Connection & Performance
- [C12. Set timeouts](c12-timeouts)
- [C13. Set an overall timeout](c13-max-timeout)
- [C14. Understand connection reuse and Keep-Alive behavior](c14-keep-alive)
- [C15. Enable compression](c15-compression)
- [C16. Send requests through a proxy](c16-proxy)
### Error Handling & Debugging
- [C17. Handle error codes](c17-error-codes)
- [C18. Handle SSL errors](c18-ssl-errors)
- [C19. Set up client logging](c19-client-logger)
## Server
### Basics
- [S01. Register GET / POST / PUT / DELETE handlers](s01-handlers)
- [S02. Receive JSON requests and return JSON responses](s02-json-api)
- [S03. Use path parameters](s03-path-params)
- [S04. Set up a static file server](s04-static-files)
### Streaming & Files
- [S05. Stream a large file in the response](s05-stream-response)
- [S06. Return a file download response](s06-download-response)
- [S07. Receive multipart data as a stream](s07-multipart-reader)
- [S08. Return a compressed response](s08-compress-response)
### Handler Chain
- [S09. Add pre-processing to all routes](s09-pre-routing)
- [S10. Add response headers with a post-routing handler](s10-post-routing)
- [S11. Authenticate per route with a pre-request handler](s11-pre-request)
- [S12. Pass data between handlers with `res.user_data`](s12-user-data)
Handlers take `(const Request&, Response&)`. Use `res.set_content()` to set the body and Content-Type, and `res.status` for the status code. `listen()` starts the server and blocks.
To add a response header, use `res.set_header("Name", "Value")`.
> **Note:** `listen()` is a blocking call. To run it on a different thread, wrap it in `std::thread`. If you need non-blocking startup, see [S18. Control startup order with `listen_after_bind`](s18-listen-after-bind).
> To use path parameters like `/users/:id`, see [S03. Use path parameters](s03-path-params).
title: "S02. Receive a JSON Request and Return a JSON Response"
order: 21
status: "draft"
---
cpp-httplib doesn't include a JSON parser. On the server side, combine it with something like [nlohmann/json](https://github.com/nlohmann/json). The examples below use `nlohmann/json`.
`req.body` is a plain `std::string`, so you pass it straight to your JSON library. For the response, `dump()` to a string and set the Content-Type to `application/json`.
> **Note:** A large JSON body ends up entirely in `req.body`, which means it all sits in memory. For huge payloads, consider streaming reception — see [S07. Receive multipart data as a stream](s07-multipart-reader).
> For the client side, see [C02. Send and receive JSON](c02-json).
A request to `/users/42` fills `req.path_params["id"]` with `"42"`. `path_params` is a `std::unordered_map<std::string, std::string>`, so use `at()` to read it.
To serve static files like HTML, CSS, and images, use `set_mount_point()`. Just map a URL path to a local directory, and the whole directory becomes accessible.
## Basic usage
```cpp
httplib::Server svr;
svr.set_mount_point("/", "./public");
svr.listen("0.0.0.0", 8080);
```
`./public/index.html` is now reachable at `http://localhost:8080/index.html`, and `./public/css/style.css` at `http://localhost:8080/css/style.css`. The directory layout maps directly to URLs.
## Multiple mount points
You can register more than one mount point.
```cpp
svr.set_mount_point("/", "./public");
svr.set_mount_point("/assets", "./dist/assets");
svr.set_mount_point("/uploads", "./var/uploads");
```
You can even mount multiple directories at the same path — they're searched in registration order, and the first hit wins.
## Combine with API handlers
Static files and API handlers coexist happily. Handlers registered with `Get()` and friends take priority; the mount points are searched only when nothing matches.
```cpp
svr.Get("/api/users", [](const auto &req, auto &res) {
res.set_content("[]", "application/json");
});
svr.set_mount_point("/", "./public");
```
This gives you an SPA-friendly setup: `/api/*` hits the handlers, everything else is served from `./public/`.
## Add MIME types
cpp-httplib ships with a built-in extension-to-Content-Type map, but you can add your own.
> **Warning:** The static file server methods are **not thread-safe**. Don't call them after `listen()` — configure everything before starting the server.
> For download-style responses, see [S06. Return a file download response](s06-download-response).
When the response is a huge file or data generated on the fly, loading the whole thing into memory isn't realistic. Use `Response::set_content_provider()` to produce data in chunks as you send it.
auto data = read_range_from_file("large.bin", offset, length);
sink.write(data.data(), data.size());
return true;
});
});
```
The lambda is called repeatedly with `offset` and `length`. Read just that range and write it to `sink`. Only a small chunk sits in memory at any given time.
## Just send a file
If you only want to serve a file, `set_file_content()` is far simpler.
It streams internally, so even huge files are safe. Omit the Content-Type and it's guessed from the extension.
## When the size is unknown — chunked transfer
For data generated on the fly, where you don't know the total size up front, use `set_chunked_content_provider()`. It's sent with HTTP chunked transfer encoding.
> **Note:** The provider lambda is called multiple times. Watch out for the lifetime of captured variables — wrap them in a `std::shared_ptr` if needed.
> To serve the file as a download, see [S06. Return a file download response](s06-download-response).
To force a browser to show a **download dialog** instead of rendering inline, send a `Content-Disposition` header. There's no special cpp-httplib API for this — it's just a header.
> **Note:** Some browsers will trigger a download based on Content-Type alone, even without `Content-Disposition`. Conversely, setting `inline` tries to render the content in the browser when possible.
A naive upload handler puts the whole request into `req.body`, which blows up memory for large files. Use `HandlerWithContentReader` to receive the body chunk by chunk.
cpp-httplib automatically compresses response bodies when the client indicates support via `Accept-Encoding`. The handler doesn't need to do anything special. Supported encodings are gzip, Brotli, and Zstd.
## Build-time setup
To enable compression, define the relevant macros before including `httplib.h`:
```cpp
#define CPPHTTPLIB_ZLIB_SUPPORT // gzip
#define CPPHTTPLIB_BROTLI_SUPPORT // brotli
#define CPPHTTPLIB_ZSTD_SUPPORT // zstd
#include <httplib.h>
```
You'll also need to link `zlib`, `brotli`, and `zstd` respectively. Enable only what you need.
That's it. If the client sent `Accept-Encoding: gzip`, cpp-httplib compresses the response with gzip automatically. `Content-Encoding: gzip` and `Vary: Accept-Encoding` are added for you.
## Encoding priority
When the client accepts multiple encodings, cpp-httplib picks in this order (among those enabled at build time): Brotli → Zstd → gzip. Your code doesn't need to care — you always get the most efficient option available.
## Streaming responses are compressed too
Streaming responses via `set_chunked_content_provider()` get the same automatic compression.
> **Note:** Tiny responses barely benefit from compression and just waste CPU time. cpp-httplib skips compression for bodies that are too small to bother with.
> For the client-side counterpart, see [C15. Enable compression](c15-compression).
If auth fails, return `Handled` to respond with 401 immediately. If it passes, return `Unhandled` and let routing take over.
## For per-route auth
If you want different auth rules per route rather than a single global check, `set_pre_request_handler()` is a better fit. See [S11. Authenticate per route with a pre-request handler](s11-pre-request).
> **Note:** If all you want is to modify the response, `set_post_routing_handler()` is the right tool. See [S10. Add response headers with a post-routing handler](s10-post-routing).
title: "S10. Add Response Headers with a Post-Routing Handler"
order: 29
status: "draft"
---
Sometimes you want to add shared headers to the response after the handler has run — CORS headers, security headers, a request ID, and so on. That's what `set_post_routing_handler()` is for.
The post-routing handler runs **after the route handler, before the response is sent**. From here you can call `res.set_header()` or `res.headers.erase()` to add or remove headers across every response in one place.
No matter which handler produced the response, the same headers get attached.
> **Note:** The post-routing handler also runs for responses that didn't match any route and for responses from error handlers. That's exactly what you want when you need certain headers on every response, guaranteed.
title: "S11. Authenticate Per Route with a Pre-Request Handler"
order: 30
status: "draft"
---
The `set_pre_routing_handler()` from [S09. Add pre-processing to all routes](s09-pre-routing) runs **before routing**, so it has no idea which route matched. When you want per-route behavior, `set_pre_request_handler()` is what you need.
## Pre-routing vs. pre-request
| Hook | When it runs | Route info |
| --- | --- | --- |
| `set_pre_routing_handler` | Before routing | Not available |
| `set_pre_request_handler` | After routing, right before the route handler | Available via `req.matched_route` |
In a pre-request handler, `req.matched_route` holds the **pattern string** that matched. You can vary behavior based on the route definition itself.
`matched_route` is the pattern **before** path parameters are expanded (e.g. `/admin/users/:id`). You compare against the route definition, not the actual request path, so IDs or names don't throw you off.
## Return values
Same as pre-routing — return `HandlerResponse`.
- `Unhandled`: continue (the route handler runs)
- `Handled`: we're done, skip the route handler
## Passing auth info to the route handler
To pass decoded user info into the route handler, use `res.user_data`. See [S12. Pass data between handlers with `res.user_data`](s12-user-data).
title: "S12. Pass Data Between Handlers with res.user_data"
order: 31
status: "draft"
---
Say your pre-request handler decodes an auth token and you want the route handler to use the result. That "data handoff between handlers" is what `res.user_data` is for — it holds values of arbitrary types.
`user_data.set()` stores a value of any type, and `user_data.get<T>()` retrieves it. If you give the wrong type you get `nullptr` back — so be careful.
## Typical value types
Strings, numbers, structs, `std::shared_ptr` — anything copyable or movable works.
The usual flow is: set it in `set_pre_routing_handler()` or `set_pre_request_handler()`, read it in the route handler. Pre-request runs after routing, so you can combine it with `req.matched_route` to set values only for specific routes.
## A gotcha
`user_data` lives on `Response`, not `Request`. That's because handlers get `Response&` (mutable) but only `const Request&`. It looks odd at first, but it makes sense once you think of it as "the mutable context shared between handlers."
> **Warning:**`user_data.get<T>()` returns `nullptr` when the type doesn't match. Use the exact same type on set and get. Storing as `AuthUser` and fetching as `const AuthUser` won't work.
auto body = "<h1>Error " + std::to_string(res.status) + "</h1>";
res.set_content(body, "text/html");
});
```
The error handler runs right before an error response is sent — any time `res.status` is 4xx or 5xx. Replace the body with `res.set_content()` and every error response uses the same template.
Now every error comes back in a consistent JSON shape.
> **Note:**`set_error_handler()` also fires for 500 responses caused by exceptions thrown from a route handler. To get at the exception itself, combine it with `set_exception_handler()`. See [S14. Catch exceptions](s14-exception-handler).
When a route handler throws, cpp-httplib keeps the server running and responds with 500. By default, though, very little of the error information reaches the client. `set_exception_handler()` lets you intercept exceptions and build your own response.
The handler receives a `std::exception_ptr`. The idiomatic move is to rethrow it with `std::rethrow_exception()` and catch by type. You can vary status code and message based on the exception type.
## Branch on custom exception types
If you throw your own exception types, you can map them to 400 or 404 responses.
```cpp
struct NotFound : std::runtime_error {
using std::runtime_error::runtime_error;
};
struct BadRequest : std::runtime_error {
using std::runtime_error::runtime_error;
};
svr.set_exception_handler(
[](const auto &req, auto &res, std::exception_ptr ep) {
try {
std::rethrow_exception(ep);
} catch (const NotFound &e) {
res.status = 404;
res.set_content(e.what(), "text/plain");
} catch (const BadRequest &e) {
res.status = 400;
res.set_content(e.what(), "text/plain");
} catch (const std::exception &e) {
res.status = 500;
res.set_content("internal error", "text/plain");
}
});
```
Now throwing `NotFound("user not found")` inside a handler is enough to return 404. No per-handler try/catch needed.
## Relationship with set_error_handler
`set_exception_handler()` runs the moment the exception is thrown. After that, if `res.status` is 4xx or 5xx, `set_error_handler()` also runs. The order is `exception_handler` → `error_handler`. Think of their roles as:
- **Exception handler**: interpret the exception, set the status and message
- **Error handler**: see the status and wrap it in the shared template
> **Note:** Without an exception handler, cpp-httplib returns a default 500 response and the exception details never make it to logs. Always set one for anything you want to debug.
To log the requests the server receives and the responses it returns, use `Server::set_logger()`. The callback fires once per completed request, making it the foundation for access logs and metrics collection.
For more on `user_data`, see [S12. Pass data between handlers with `res.user_data`](s12-user-data).
> **Note:** The logger runs synchronously on the same thread as request processing. Heavy work inside it hurts throughput — push it to a queue and process asynchronously if you need anything expensive.
title: "S16. Detect When the Client Has Disconnected"
order: 35
status: "draft"
---
During a long-running response, the client might close the connection. There's no point continuing to do work no one's waiting for. In cpp-httplib, check `req.is_connection_closed()`.
When you detect a disconnect, call `sink.done()` to stop the provider from being called again.
## How often should you check?
The call itself is cheap, but calling it in a tight inner loop doesn't add much value. Check at **boundaries where interrupting is safe** — after producing a chunk, after a database query, etc.
> **Warning:**`is_connection_closed()` is not guaranteed to reflect reality instantly. Because of how TCP works, sometimes you only notice the disconnect when you try to send. Don't expect pixel-perfect real-time detection — think of it as "we'll notice eventually."
Standing up a test server often hits port conflicts. With `bind_to_any_port()`, you let the OS pick a free port and then read back which one it gave you.
## Basic usage
```cpp
httplib::Server svr;
svr.Get("/", [](const auto &req, auto &res) {
res.set_content("hello", "text/plain");
});
int port = svr.bind_to_any_port("0.0.0.0");
std::cout << "listening on port " << port << std::endl;
svr.listen_after_bind();
```
`bind_to_any_port()` is equivalent to passing `0` as the port — the OS assigns a free one. The return value is the port actually used.
After that, call `listen_after_bind()` to start accepting. You can't combine bind and listen into a single call here, so you work in two steps.
## Useful in tests
This pattern is great for tests that spin up a server and hit it.
```cpp
httplib::Server svr;
svr.Get("/ping", [](const auto &, auto &res) { res.set_content("pong", "text/plain"); });
int port = svr.bind_to_any_port("127.0.0.1");
std::thread t([&] { svr.listen_after_bind(); });
// run the test while the server is up on another thread
httplib::Client cli("127.0.0.1", port);
auto res = cli.Get("/ping");
assert(res && res->body == "pong");
svr.stop();
t.join();
```
Because the port is assigned at runtime, parallel test runs don't collide.
> **Note:**`bind_to_any_port()` returns `-1` on failure (permission errors, no available ports, etc.). Always check the return value.
> To stop the server, see [S19. Shut down gracefully](s19-graceful-shutdown).
title: "S18. Control Startup Order with listen_after_bind"
order: 37
status: "draft"
---
Normally `svr.listen("0.0.0.0", 8080)` handles bind and listen in one shot. When you need to do something between the two, split them into two calls.
## Separate bind and listen
```cpp
httplib::Server svr;
svr.Get("/", [](const auto &, auto &res) { res.set_content("ok", "text/plain"); });
if (!svr.bind_to_port("0.0.0.0", 8080)) {
std::cerr << "bind failed" << std::endl;
return 1;
}
// bind is done here. accept hasn't started yet.
drop_privileges();
signal_ready_to_parent_process();
svr.listen_after_bind(); // start the accept loop
```
`bind_to_port()` reserves the port; `listen_after_bind()` actually starts accepting. Splitting them gives you a window between the two steps.
## Common use cases
**Privilege drop**: Binding to a port under 1024 requires root. Bind as root, drop to a normal user, and all subsequent request handling runs with reduced privileges.
```cpp
svr.bind_to_port("0.0.0.0", 80);
drop_privileges();
svr.listen_after_bind();
```
**Startup notification**: Tell the parent process or systemd "I'm ready" before starting to accept connections.
**Test synchronization**: In tests, you can reliably catch "the moment the server is bound" and start the client after that.
## Check the return values
`bind_to_port()` returns `false` on failure — typically when the port is already taken. Always check it.
```cpp
if (!svr.bind_to_port("0.0.0.0", 8080)) {
std::cerr << "port already in use" << std::endl;
return 1;
}
```
`listen_after_bind()` blocks until the server stops and returns `true` on a clean shutdown.
> **Note:** To auto-pick a free port, see [S17. Bind to any available port](s17-bind-any-port). Under the hood, that's just `bind_to_any_port()` + `listen_after_bind()`.
To stop the server, call `Server::stop()`. It's safe to call even while requests are in flight, so you can wire it to SIGINT or SIGTERM for a graceful shutdown.
## Basic usage
```cpp
httplib::Server svr;
svr.Get("/", [](const auto &, auto &res) { res.set_content("ok", "text/plain"); });
`listen()` blocks, so the typical pattern is: run the server on a background thread and call `stop()` from the main thread. After `stop()`, `listen()` returns and you can `join()`.
## Shut down on a signal
Here's how to stop the server on SIGINT (Ctrl+C) or SIGTERM.
```cpp
#include <csignal>
httplib::Server svr;
// global so the signal handler can reach it
httplib::Server *g_svr = nullptr;
int main() {
svr.Get("/", [](const auto &, auto &res) { res.set_content("ok", "text/plain"); });
g_svr = &svr;
std::signal(SIGINT, [](int) { if (g_svr) g_svr->stop(); });
std::signal(SIGTERM, [](int) { if (g_svr) g_svr->stop(); });
svr.listen("0.0.0.0", 8080);
std::cout << "server stopped" << std::endl;
}
```
`stop()` is thread-safe and signal-safe — you can call it from a signal handler. Even when `listen()` is running on the main thread, the signal pulls it out cleanly.
## What happens to in-flight requests
When you call `stop()`, new connections are refused, but requests already being processed are **allowed to finish**. Once all workers drain, `listen()` returns. That's what makes it graceful.
> **Warning:** There's a wait between calling `stop()` and `listen()` returning — it's the time in-flight requests take to finish. To enforce a timeout, you'll need to add your own shutdown timer in application code.
`httplib::Server` enables HTTP/1.1 Keep-Alive automatically. From the client's perspective, connections are reused — so they don't pay the TCP handshake cost on every request. When you need to tune the behavior, there are two setters.
## What you can configure
| API | Default | Meaning |
| --- | --- | --- |
| `set_keep_alive_max_count` | 100 | Max requests served over a single connection |
| `set_keep_alive_timeout` | 5s | How long an idle connection is kept before closing |
## Basic usage
```cpp
httplib::Server svr;
svr.set_keep_alive_max_count(20);
svr.set_keep_alive_timeout(10); // 10 seconds
svr.listen("0.0.0.0", 8080);
```
`set_keep_alive_timeout()` also has a `std::chrono` overload.
```cpp
using namespace std::chrono_literals;
svr.set_keep_alive_timeout(10s);
```
## Tuning ideas
**Too many idle connections eating resources**
Shorten the timeout so idle connections drop and release their worker threads.
```cpp
svr.set_keep_alive_timeout(2s);
```
**API is hammered and you want max reuse**
Raising the per-connection request cap improves benchmark numbers.
```cpp
svr.set_keep_alive_max_count(1000);
```
**Never reuse connections**
Set `set_keep_alive_max_count(1)` and every request gets its own connection. Mostly only useful for debugging or compatibility testing.
## Relationship with the thread pool
A Keep-Alive connection holds a worker thread for its entire lifetime. If `connections × concurrent requests` exceeds the thread pool size, new requests wait. For thread counts, see [S21. Configure the thread pool](s21-thread-pool).
> **Note:** For the client side, see [C14. Understand connection reuse and Keep-Alive behavior](c14-keep-alive). Even when the server closes the connection on timeout, the client reconnects automatically.
cpp-httplib serves requests from a thread pool. By default, the base thread count is the greater of `std::thread::hardware_concurrency() - 1` and `8`, and it can scale up dynamically to 4× that. To set thread counts explicitly, provide your own factory via `new_task_queue`.
## Set thread counts
```cpp
httplib::Server svr;
svr.new_task_queue = [] {
return new httplib::ThreadPool(/*base_threads=*/8, /*max_threads=*/64);
};
svr.listen("0.0.0.0", 8080);
```
The factory is a lambda returning a `TaskQueue*`. Pass `base_threads` and `max_threads` to `ThreadPool` and the pool scales between them based on load. Idle threads exit after a timeout (3 seconds by default).
## Also cap the queue
The pending queue can eat memory if it grows unchecked. You can cap it too.
```cpp
svr.new_task_queue = [] {
return new httplib::ThreadPool(
/*base_threads=*/12,
/*max_threads=*/0, // disable dynamic scaling
/*max_queued_requests=*/18);
};
```
`max_threads=0` disables dynamic scaling — you get a fixed `base_threads`. Requests that don't fit in `max_queued_requests` are rejected.
## Use your own thread pool
You can plug in a fully custom thread pool by subclassing `TaskQueue` and returning it from the factory.
svr.new_task_queue = [] { return new MyTaskQueue(12); };
```
Handy when you already have a thread pool in your project and want to keep thread management unified.
## Compile-time tuning
You can set the defaults with macros if you want compile-time configuration.
```cpp
#define CPPHTTPLIB_THREAD_POOL_COUNT 16 // base thread count
#define CPPHTTPLIB_THREAD_POOL_MAX_COUNT 128 // max thread count
#define CPPHTTPLIB_THREAD_POOL_IDLE_TIMEOUT 5 // seconds before idle threads exit
#include <httplib.h>
```
> **Note:** A WebSocket connection holds a worker thread for its entire lifetime. For lots of simultaneous WebSocket connections, enable dynamic scaling (e.g. `ThreadPool(8, 64)`).
When you want to talk only to other processes on the same host, a Unix domain socket is a nice fit. It avoids TCP overhead and uses filesystem permissions for access control. Local IPC and services sitting behind a reverse proxy are classic use cases.
## Server side
```cpp
httplib::Server svr;
svr.set_address_family(AF_UNIX);
svr.Get("/", [](const auto &, auto &res) {
res.set_content("hello from unix socket", "text/plain");
});
svr.listen("/tmp/httplib.sock", 80);
```
Call `set_address_family(AF_UNIX)` first, then pass the socket file path as the first argument to `listen()`. The port number is unused but required by the signature — pass any value.
## Client side
```cpp
httplib::Client cli("/tmp/httplib.sock");
cli.set_address_family(AF_UNIX);
auto res = cli.Get("/");
if (res) {
std::cout << res->body << std::endl;
}
```
Pass the socket file path to the `Client` constructor and call `set_address_family(AF_UNIX)`. Everything else works like a normal HTTP request.
## When to use it
- **Behind a reverse proxy**: An nginx-to-backend setup over a Unix socket is faster than TCP and sidesteps port management
- **Local-only APIs**: IPC between tools that shouldn't be reachable from outside
- **In-container IPC**: Process-to-process communication within the same pod or container
- **Dev environments**: No more worrying about port conflicts
## Clean up the socket file
A Unix domain socket creates a real file in the filesystem. It doesn't get removed on shutdown, so delete it before starting if needed.
```cpp
std::remove("/tmp/httplib.sock");
svr.listen("/tmp/httplib.sock", 80);
```
## Permissions
You control who can connect via the socket file's permissions.
```cpp
svr.listen("/tmp/httplib.sock", 80);
// from another process or thread
chmod("/tmp/httplib.sock", 0660); // owner and group only
```
> **Warning:** Some Windows versions support AF_UNIX, but the implementation and behavior differ by platform. Test thoroughly before running cross-platform in production.
title: "T01. Choosing Between OpenSSL, mbedTLS, and wolfSSL"
order: 42
status: "draft"
---
cpp-httplib doesn't ship its own TLS implementation — it uses one of three backends that you pick at build time via a macro.
| Backend | Macro | Character |
| --- | --- | --- |
| OpenSSL | `CPPHTTPLIB_OPENSSL_SUPPORT` | Most widely used, richest feature set |
| mbedTLS | `CPPHTTPLIB_MBEDTLS_SUPPORT` | Lightweight, aimed at embedded |
| wolfSSL | `CPPHTTPLIB_WOLFSSL_SUPPORT` | Embedded-friendly, commercial support available |
## Build-time selection
Define the macro for your chosen backend before including `httplib.h`:
```cpp
#define CPPHTTPLIB_OPENSSL_SUPPORT
#include <httplib.h>
```
You'll also need to link against the backend's libraries (`libssl`, `libcrypto`, `libmbedtls`, `libwolfssl`, etc.).
## Which to pick
**When in doubt, OpenSSL**
It has the most features and the best documentation. For normal server use or Linux desktop apps, start here — you probably won't need anything else.
**To shrink binary size or target embedded**
mbedTLS or wolfSSL are a better fit. They're far more compact than OpenSSL and run on memory-constrained devices.
**When you need commercial support**
wolfSSL offers commercial licensing and support. If you're shipping in a product, it's worth considering.
## Supporting multiple backends
The usual approach is to treat each backend as a build variant and recompile the same source with different macros. cpp-httplib smooths over most of the API differences, but the backends are not 100% identical — always test.
## APIs that work across all backends
Certificate verification control, standing up an SSLServer, reading the peer certificate — these all share the same API across backends:
- [T02. Control SSL certificate verification](t02-cert-verification)
- [T03. Start an SSL/TLS server](t03-ssl-server)
- [T05. Access the peer certificate on the server](t05-peer-cert)
> **Note:** On macOS with an OpenSSL-family backend, cpp-httplib automatically loads root certificates from the system keychain (via `CPPHTTPLIB_USE_CERTS_FROM_MACOSX_KEYCHAIN`, on by default). To disable this, define `CPPHTTPLIB_DISABLE_MACOSX_AUTOMATIC_ROOT_CERTIFICATES`.
title: "T02. Control SSL Certificate Verification"
order: 43
status: "draft"
---
By default, an HTTPS client verifies the server certificate — it uses the OS root certificate store to check the chain and the hostname. Here are the APIs for changing that behavior.
## Specify a custom CA certificate
When connecting to a server whose certificate is signed by an internal CA, use `set_ca_cert_path()`.
The first argument is the CA certificate file; the second is an optional CA directory. With the OpenSSL backend, you can also pass an `X509_STORE*` directly via `set_ca_cert_store()`.
That's all it takes to disable chain verification.
> **Warning:** Disabling certificate verification removes protection against man-in-the-middle attacks. **Never do this in production.** If you find yourself needing it outside of dev/test, pause and make sure you're not doing something wrong.
## Disable hostname verification only
There's an in-between option: verify the certificate chain, but skip the hostname check. Useful when you need to reach a server whose cert CN/SAN doesn't match the request's hostname.
```cpp
cli.enable_server_hostname_verification(false);
```
The certificate itself is still validated, so this is safer than fully disabling verification — but still not recommended in production.
## Use the OS cert store as-is
On most Linux distributions, root certificates live in a single file like `/etc/ssl/certs/ca-certificates.crt`. cpp-httplib reads the OS default store at startup, so for most servers you don't need to configure anything.
> The same APIs work on the mbedTLS and wolfSSL backends. For choosing between backends, see [T01. Choosing between OpenSSL, mbedTLS, and wolfSSL](t01-tls-backends).
> For details on diagnosing failures, see [C18. Handle SSL errors](c18-ssl-errors).
To stand up an HTTPS server, use `httplib::SSLServer` instead of `httplib::Server`. Pass a certificate and private key to the constructor, and you get back something that works exactly like `Server`.
## Basic usage
```cpp
#define CPPHTTPLIB_OPENSSL_SUPPORT
#include <httplib.h>
int main() {
httplib::SSLServer svr("cert.pem", "key.pem");
svr.Get("/", [](const auto &req, auto &res) {
res.set_content("hello over TLS", "text/plain");
});
svr.listen("0.0.0.0", 443);
}
```
Pass the server certificate (PEM format) and private key file paths to the constructor. That's all you need for a TLS-enabled server. Registering handlers and calling `listen()` work the same as with `Server`.
## Password-protected private keys
The fifth argument is the private key password.
```cpp
httplib::SSLServer svr("cert.pem", "key.pem",
nullptr, nullptr, "password");
```
The third and fourth arguments are for client certificate verification (mTLS, see [T04. Configure mTLS](t04-mtls)). For now, pass `nullptr`.
## Load PEM data from memory
When you want to load certs from memory instead of files, use the `PemMemory` struct.
```cpp
httplib::SSLServer::PemMemory pem{};
pem.cert_pem = cert_data.data();
pem.cert_pem_len = cert_data.size();
pem.key_pem = key_data.data();
pem.key_pem_len = key_data.size();
httplib::SSLServer svr(pem);
```
Handy when you pull certificates from environment variables or a secrets manager.
## Rotate certificates
Before a certificate expires, you may want to swap it out without restarting the server. That's what `update_certs_pem()` is for.
```cpp
svr.update_certs_pem(new_cert_pem, new_key_pem);
```
Existing connections keep using the old cert; new connections use the new one.
## Generating a test certificate
For a throwaway self-signed cert, use the `openssl` CLI.
In production, use certificates from Let's Encrypt or your internal CA.
> **Warning:** Binding an HTTPS server to port 443 requires root. For a safe way to do that, see the privilege-drop pattern in [S18. Control startup order with `listen_after_bind`](s18-listen-after-bind).
> For mutual TLS (client certificates), see [T04. Configure mTLS](t04-mtls).
Regular TLS verifies the server certificate only. **mTLS** (mutual TLS) adds the other direction: the client presents a certificate too, and the server verifies it. It's common for zero-trust API-to-API traffic and internal system authentication.
## Server side
Pass the CA used to verify client certificates as the third (and fourth) argument to `SSLServer`.
```cpp
httplib::SSLServer svr(
"server-cert.pem", // server certificate
"server-key.pem", // server private key
"client-ca.pem", // CA that signs valid client certs
With this, any connection whose client certificate isn't signed by `client-ca.pem` is rejected at the handshake. By the time a handler runs, the client is already authenticated.
## Configure with in-memory PEM
```cpp
httplib::SSLServer::PemMemory pem{};
pem.cert_pem = server_cert.data();
pem.cert_pem_len = server_cert.size();
pem.key_pem = server_key.data();
pem.key_pem_len = server_key.size();
pem.client_ca_pem = client_ca.data();
pem.client_ca_pem_len = client_ca.size();
httplib::SSLServer svr(pem);
```
This is the clean way when you load certificates from environment variables or a secrets manager.
## Client side
On the client side, pass the client certificate and key to `SSLClient`.
```cpp
httplib::SSLClient cli("api.example.com", 443,
"client-cert.pem",
"client-key.pem");
auto res = cli.Get("/");
```
Note you're using `SSLClient` directly, not `Client`. If the private key has a password, pass it as the fifth argument.
## Read client info from a handler
To see which client connected from inside a handler, use `req.peer_cert()`. Details in [T05. Access the peer certificate on the server](t05-peer-cert).
## Use cases
- **Microservice-to-microservice calls**: Issue a cert per service, use the cert as identity
- **IoT device management**: Burn a cert into each device and use it to gate API access
- **An alternative to internal VPN**: Put cert-based auth in front of public endpoints so internal resources can be reached safely
> **Note:** Issuing and revoking client certificates is more operational work than password-based auth. You'll need either an internal PKI setup or an automated flow using ACME-family tools.
Combined with a pre-request handler, you can keep all authorization logic in one place. See [S11. Authenticate per route with a pre-request handler](s11-pre-request).
## SNI (Server Name Indication)
cpp-httplib handles SNI automatically. If one server hosts multiple domains, SNI is used under the hood — but normally handlers don't need to care.
> **Warning:**`req.peer_cert()` only returns a meaningful value when mTLS is enabled and the client actually presented a certificate. For plain TLS, you get an empty `PeerCert`. Always do the `bool` check before using it.
> To set up mTLS, see [T04. Configure mTLS](t04-mtls).
title: "W01. Implement a WebSocket Echo Server and Client"
order: 51
status: "draft"
---
WebSocket is a protocol for **two-way** messaging between client and server. cpp-httplib provides APIs for both sides. Let's start with the simplest example: an echo server.
Register a WebSocket handler with `svr.WebSocket()`. By the time the handler runs, the WebSocket handshake is already complete. Inside the loop, just `ws.read()` and `ws.send()` to get a working echo.
The `std::string` overload sends as **text**; the `const char*` + size overload sends as **binary**. A bit subtle, but once you know it, it's intuitive. See [W04. Send and receive binary frames](w04-websocket-binary) for details.
## Thread pool implications
A WebSocket handler holds its worker thread for the entire life of the connection — one connection per thread. For many concurrent clients, configure a dynamic thread pool.
```cpp
svr.new_task_queue = [] {
return new httplib::ThreadPool(8, 128);
};
```
See [S21. Configure the thread pool](s21-thread-pool).
> **Note:** To run WebSocket over HTTPS, use `httplib::SSLServer` instead of `httplib::Server` — the same `WebSocket()` handler just works. On the client side, use a `wss://` URL.
WebSocket connections stay open for a long time, and proxies or load balancers will sometimes drop them for being "idle." To prevent that, you periodically send Ping frames to keep the connection alive. cpp-httplib can do this for you automatically.
## Server side
```cpp
svr.set_websocket_ping_interval(30); // ping every 30 seconds
svr.WebSocket("/chat", [](const auto &req, auto &ws) {
// ...
});
```
Just pass the interval in seconds. Every WebSocket connection this server accepts will be pinged on that interval.
The default interval is set by the build-time macro `CPPHTTPLIB_WEBSOCKET_PING_INTERVAL_SECOND`. Usually you won't need to change it, but adjust downward if you're dealing with an aggressive proxy.
## What about Pong?
The WebSocket protocol requires that Ping frames are answered with Pong frames. cpp-httplib responds to Pings automatically — you don't need to think about it in application code.
## Picking an interval
| Environment | Suggested |
| --- | --- |
| Normal internet | 30–60s |
| Strict proxies (e.g. AWS ALB) | 15–30s |
| Mobile networks | 60s+ (too short drains battery) |
Too short wastes bandwidth; too long and connections get dropped. As a rule of thumb, target about **half the idle timeout** of whatever's between you and the client.
> **Warning:** A very short ping interval spawns background work per connection and increases CPU usage. For servers with many connections, keep the interval modest.
## Detecting an unresponsive peer
Sending pings alone doesn't tell you anything if the peer just silently dies — the TCP socket might still look open while the process on the other end is long gone. To catch that, enable the max-missed-pongs check: if N consecutive pings go unanswered, the connection is closed.
```cpp
cli.set_websocket_max_missed_pongs(2); // close after 2 consecutive unacked pings
```
The server side has the same `set_websocket_max_missed_pongs()`.
With a 30-second ping interval and `max_missed_pongs = 2`, a dead peer is detected within roughly 60 seconds and the connection is closed with `CloseStatus::GoingAway` and the reason `"pong timeout"`.
The counter is reset whenever `read()` consumes an incoming Pong frame, so this only works if your code is actively calling `read()` in a loop — which is what a normal WebSocket client does anyway.
### Why the default is 0
`max_missed_pongs` defaults to `0`, which means "never close the connection because of missing pongs." Pings are still sent on the heartbeat interval, but their responses aren't checked. If you want unresponsive-peer detection, set it explicitly to `1` or higher.
Even with `0`, a dead connection won't linger forever: while your code is inside `read()`, `CPPHTTPLIB_WEBSOCKET_READ_TIMEOUT_SECOND` (default **300 seconds = 5 minutes**) acts as a backstop and `read()` fails if no frame arrives in time. Think of `max_missed_pongs` as the knob for detecting an unresponsive peer **faster** than that.
> For handling a closed connection, see [W03. Handle connection close](w03-websocket-close).
A WebSocket ends when either side closes it explicitly, or when the network drops. Handle close cleanly, and your cleanup and reconnect logic stays tidy.
## Detect a closed connection
When `ws.read()` returns `ReadResult::Fail`, the connection is gone — either cleanly or with an error. Break out of the loop and the handler will finish.
> **Note:** On a sudden network drop, `read()` returns `Fail` with no chance to call `close()`. Put your cleanup at the end of the handler, and both paths — clean close and abrupt disconnect — end up in the same place.
WebSocket has two frame types: text and binary. JSON and plain text go in text frames; images and raw protocol bytes go in binary. In cpp-httplib, `send()` picks the right type via overload.
## How to pick a frame type
```cpp
ws.send(std::string("Hello")); // text
ws.send("Hello", 5); // binary
ws.send(binary_data, binary_data_size); // binary
```
The `std::string` overload sends as **text**. The `const char*` + size overload sends as **binary**. A bit subtle, but once you know it, it sticks.
If you have a `std::string` and want to send it as binary, pass `.data()` and `.size()` explicitly.
```cpp
std::string raw = build_binary_payload();
ws.send(raw.data(), raw.size()); // binary frame
```
## Detect frame type on receive
The return value of `ws.read()` tells you whether the received frame was text or binary.
Binary frames still come back in a `std::string`, but treat its contents as raw bytes — use `msg.data()` and `msg.size()`.
## When binary is the right call
- **Images, video, audio**: No Base64 overhead
- **Custom protocols**: protobuf, MessagePack, or any structured binary format
- **Game networking**: When latency matters
- **Sensor data streams**: Push numeric arrays directly
## Ping is binary-ish, but hidden
WebSocket Ping/Pong frames are close cousins of binary frames at the opcode level, but cpp-httplib handles them automatically — you don't touch them. See [W02. Set a WebSocket heartbeat](w02-websocket-ping).
## Example: send an image
```cpp
// Server: push an image
svr.WebSocket("/image", [](const auto &req, auto &ws) {
You can mix text and binary in the same connection. A common pattern: JSON for control messages, binary for the actual data — you get efficient handling of metadata and payload both.
> **Note:** WebSocket frames don't have an infinite size limit. For very large data, chunk it in your application code. cpp-httplib can handle a big frame in one shot, but it does load it all into memory at once.
[cpp-httplib](https://github.com/yhirose/cpp-httplib) is an HTTP/HTTPS library for C++. Just copy a single header file, [`httplib.h`](https://github.com/yhirose/cpp-httplib/raw/refs/tags/latest/httplib.h), and you're ready to go.
When you need a quick HTTP server or client in C++, you want something that just works. That's exactly why I built cpp-httplib. You can start writing both servers and clients in just a few lines of code.
The API uses a lambda-based design that feels natural. It runs anywhere you have a C++11 or later compiler. Windows, macOS, Linux — use whatever environment you already have.
HTTPS works too. Just link OpenSSL or mbedTLS, and both server and client gain TLS support. Content-Encoding (gzip, Brotli, etc.), file uploads, and other features you actually need in real-world development are all included. WebSocket is also supported.
Under the hood, it uses blocking I/O with a thread pool. It's not built for handling massive numbers of simultaneous connections. But for API servers, embedded HTTP in tools, mock servers for testing, and many other use cases, it delivers solid performance.
"Solve today's problem, today." That's the kind of simplicity cpp-httplib aims for.
## Documentation
- [A Tour of cpp-httplib](tour/) — A step-by-step tutorial covering the basics. Start here if you're new
- [Building a Desktop LLM App](llm-app/) — A hands-on guide to building a desktop app with llama.cpp, step by step
## Stay Tuned
- [Cookbook](cookbook/) — A collection of recipes organized by topic. Jump to whatever you need
Let's incrementally build a text translation REST API server using llama.cpp as the inference engine. By the end, a request like this will return a translation result.
```bash
curl -X POST http://localhost:8080/translate \
-H "Content-Type: application/json" \
-d '{"text": "The weather is nice today. Shall we go for a walk?", "target_lang": "ja"}'
```
```json
{
"translation": "今日はいい天気ですね。散歩に行きましょうか？"
}
```
The "Translation API" is just one example. By swapping out the prompt, you can adapt this to any LLM application you like, such as summarization, code generation, or a chatbot.
Here's the full list of APIs the server will provide.
| Method | Path | Description | Chapter |
| -------- | ---- | ---- | -- |
| `GET` | `/health` | Returns server status | 1 |
| `POST` | `/translate` | Translates text and returns JSON | 2 |
| `POST` | `/translate/stream` | SSE streaming on a per-token basis | 3 |
| `GET` | `/models` | Model list (available / downloaded / selected) | 4 |
| `POST` | `/models/select` | Select a model (automatically downloads if not yet downloaded) | 4 |
In this chapter, let's set up the project environment. We'll fetch the dependency libraries, create the directory structure, configure the build settings, and grab the model file, so that we're ready to start writing code in the next chapter.
| [webview/webview](https://github.com/webview/webview) | Desktop WebView (used in Chapter 6) |
cpp-httplib, nlohmann/json, and cpp-llamalib are header-only libraries. You could just download a single header file with `curl` and `#include` it, but in this book we use CMake's `FetchContent` to fetch them automatically. Declare them in `CMakeLists.txt`, and `cmake -B build` downloads and builds everything for you. webview is used in Chapter 6, so you don't need to worry about it for now.
## 1.2 Directory Structure
The final structure will look like this.
```ascii
translate-app/
├── CMakeLists.txt
├── models/
│ └── (GGUF files)
└── src/
└── main.cpp
```
We don't include library source code in the project. CMake's `FetchContent` fetches them automatically at build time, so all you need is your own code.
Let's create the project directory and initialize a git repository.
```bash
mkdir translate-app && cd translate-app
mkdir src models
git init
```
## 1.3 Obtaining the GGUF Model File
You need a model file for LLM inference. GGUF is the model format used by llama.cpp, and you can find many models on Hugging Face.
Let's start by trying a small model. The quantized version of Google's Gemma 2 2B (~1.6 GB) is a good starting point. It's lightweight but supports multiple languages and works well for translation tasks.
In Chapter 4, we'll add the ability to download models from within the app using cpp-httplib's client functionality.
## 1.4 CMakeLists.txt
Create a `CMakeLists.txt` in the project root. By declaring dependencies with `FetchContent`, CMake will automatically download and build them for you.
`FetchContent_Declare` tells CMake where to find each library, and `FetchContent_MakeAvailable` fetches and builds them. The first `cmake -B build` will take some time because it downloads all libraries and builds llama.cpp, but subsequent runs will use the cache.
Just link with `target_link_libraries`, and each library's CMake configuration sets up include paths and build settings for you.
## 1.5 Creating the Skeleton Code
We'll use this skeleton code as a base and add functionality chapter by chapter.
<!-- data-file="main.cpp" -->
```cpp
// src/main.cpp
#include <httplib.h>
#include <nlohmann/json.hpp>
#include <csignal>
#include <iostream>
using json = nlohmann::json;
httplib::Server svr;
// Graceful shutdown on `Ctrl+C`
void signal_handler(int sig) {
if (sig == SIGINT || sig == SIGTERM) {
std::cout << "\nReceived signal, shutting down gracefully...\n";
svr.stop();
}
}
int main() {
// Log requests and responses
svr.set_logger([](const auto &req, const auto &res) {
// Allow the server to be stopped with `Ctrl+C` (`SIGINT`) or `kill` (`SIGTERM`)
signal(SIGINT, signal_handler);
signal(SIGTERM, signal_handler);
// Start the server
std::cout << "Listening on http://127.0.0.1:8080" << std::endl;
svr.listen("127.0.0.1", 8080);
}
```
## 1.6 Building and Verifying
Build the project, start the server, and verify that requests work with curl.
```bash
cmake -B build
cmake --build build -j
./build/translate-server
```
From another terminal, try it with curl.
```bash
curl http://localhost:8080/health
# => {"status":"ok"}
```
If you see JSON come back, the setup is complete.
## Next Chapter
Now that the environment is set up, in the next chapter we'll implement the translation REST API on top of this skeleton. We'll run inference with llama.cpp and expose it as an HTTP endpoint with cpp-httplib.
**Next:** [Integrating llama.cpp to Build a REST API](../ch02-rest-api)
title: "2. Integrating llama.cpp to Build a REST API"
order: 2
---
In the skeleton from Chapter 1, `/translate` simply returned `"TODO"`. In this chapter we integrate llama.cpp inference and turn it into an API that actually returns translation results.
Calling the llama.cpp API directly makes the code quite long, so we use a thin wrapper library called [cpp-llamalib](https://github.com/yhirose/cpp-llamalib). It lets you load a model and run inference in just a few lines, keeping the focus on cpp-httplib.
## 2.1 Initializing the LLM
Simply pass the path to a model file to `llamalib::Llama`, and model loading, context creation, and sampler configuration are all taken care of. If you downloaded a different model in Chapter 1, adjust the path accordingly.
```cpp
#include <cpp-llamalib.h>
int main() {
auto llm = llamalib::Llama{"models/gemma-2-2b-it-Q4_K_M.gguf"};
// LLM inference takes time, so set a longer timeout (default is 5 seconds)
svr.set_read_timeout(300);
svr.set_write_timeout(300);
// ... Build and start the HTTP server ...
}
```
If you want to change the number of GPU layers, context length, or other settings, you can specify them via `llamalib::Options`.
```cpp
auto llm = llamalib::Llama{"models/gemma-2-2b-it-Q4_K_M.gguf", {
.n_gpu_layers = 0, // CPU only
.n_ctx = 4096,
}};
```
## 2.2 The `/translate` Handler
We replace the handler that returned dummy JSON in Chapter 1 with actual inference.
`llm.chat()` can throw exceptions during inference (for example, when the context length is exceeded). By catching them with `try/catch` and returning the error as JSON, we prevent the server from crashing.
## 2.3 Complete Code
Here is the finished code with all the changes so far.
// Allow the server to be stopped with `Ctrl+C` (`SIGINT`) or `kill` (`SIGTERM`)
signal(SIGINT, signal_handler);
signal(SIGTERM, signal_handler);
// Start the server (blocks until `stop()` is called)
std::cout << "Listening on http://127.0.0.1:8080" << std::endl;
svr.listen("127.0.0.1", 8080);
}
```
</details>
## 2.4 Testing It Out
Rebuild and start the server, then verify that it now returns actual translation results.
```bash
cmake --build build -j
./build/translate-server
```
```bash
curl -X POST http://localhost:8080/translate \
-H "Content-Type: application/json" \
-d '{"text": "I had a great time visiting Tokyo last spring. The cherry blossoms were beautiful.", "target_lang": "ja"}'
# => {"translation":"去年の春に東京を訪れた。桜が綺麗だった。"}
```
In Chapter 1 the response was `"TODO"`, but now you get an actual translation back.
## Next Chapter
The REST API we built in this chapter waits for the entire translation to complete before sending the response, so for long texts the user has to wait with no indication of progress.
In the next chapter, we use SSE (Server-Sent Events) to stream tokens back in real time as they are generated.
**Next:** [Adding Token Streaming with SSE](../ch03-sse-streaming)
The `/translate` endpoint from Chapter 2 returned the entire translation at once after completion. This is fine for short sentences, but for longer text the user has to wait several seconds with nothing displayed.
In this chapter, we add a `/translate/stream` endpoint that uses SSE (Server-Sent Events) to return tokens in real time as they are generated. This is the same approach used by the ChatGPT and Claude APIs.
## 3.1 What is SSE?
SSE is a way to send HTTP responses as a stream. When a client sends a request, the server keeps the connection open and gradually returns events. The format is simple text.
```text
data: "去年の"
data: "春に"
data: "東京を"
data: [DONE]
```
Each line starts with `data:` and events are separated by blank lines. The Content-Type is `text/event-stream`. Tokens are sent as escaped JSON strings, so they appear enclosed in double quotes (we implement this in Section 3.3).
## 3.2 Streaming with cpp-httplib
In cpp-httplib, you can use `set_chunked_content_provider` to send responses incrementally. Each time you write to `sink.os` inside the callback, data is sent to the client.
```cpp
res.set_chunked_content_provider(
"text/event-stream",
[](size_t offset, httplib::DataSink &sink) {
sink.os << "data: hello\n\n";
sink.done();
return true;
});
```
Calling `sink.done()` ends the stream. If the client disconnects mid-stream, writing to `sink.os` will fail and `sink.os.fail()` will return `true`. You can use this to detect disconnection and abort unnecessary inference.
## 3.3 The `/translate/stream` Handler
JSON parsing and validation are the same as the `/translate` endpoint from Chapter 2. The only difference is how the response is returned. We combine the streaming callback of `llm.chat()` with `set_chunked_content_provider`.
- When you pass a callback to `llm.chat()`, it is called each time a token is generated. If the callback returns `false`, generation is aborted
- After writing to `sink.os`, you can check whether the client is still connected with `sink.os.good()`. If the client has disconnected, it returns `false` to stop inference
- Each token is escaped as a JSON string using `json(token).dump()` before sending. This is safe even for tokens containing newlines or quotes
- The first three arguments of `dump(-1, ' ', false, ...)` are the defaults. What matters is the fourth argument, `json::error_handler_t::replace`. Since the LLM returns tokens at the subword level, multi-byte characters (such as Japanese) can be split mid-character across tokens. Passing an incomplete UTF-8 byte sequence directly to `dump()` would throw an exception, so `replace` safely substitutes them. The browser reassembles the bytes on its end, so everything displays correctly
- The entire lambda is wrapped in `try/catch`. `llm.chat()` can throw exceptions for reasons such as exceeding the context window. If an exception goes uncaught inside the lambda, the server will crash, so we return the error as an SSE event instead
- `data: [DONE]` follows the OpenAI API convention to signal the end of the stream to the client
## 3.4 Complete Code
Here is the complete code with the `/translate/stream` endpoint added to the code from Chapter 2.
// Allow the server to be stopped with `Ctrl+C` (`SIGINT`) or `kill` (`SIGTERM`)
signal(SIGINT, signal_handler);
signal(SIGTERM, signal_handler);
// Start the server (blocks until `stop()` is called)
std::cout << "Listening on http://127.0.0.1:8080" << std::endl;
svr.listen("127.0.0.1", 8080);
}
```
</details>
## 3.5 Testing It Out
Build and start the server.
```bash
cmake --build build -j
./build/translate-server
```
Using curl's `-N` option to disable buffering, you can see tokens displayed in real time as they arrive.
```bash
curl -N -X POST http://localhost:8080/translate/stream \
-H "Content-Type: application/json" \
-d '{"text": "I had a great time visiting Tokyo last spring. The cherry blossoms were beautiful.", "target_lang": "ja"}'
```
```text
data: "去年の"
data: "春に"
data: "東京を"
data: "訪れた"
data: "。"
data: "桜が"
data: "綺麗だった"
data: "。"
data: [DONE]
```
You should see tokens streaming in one by one. The `/translate` endpoint from Chapter 2 continues to work as well.
## Next Chapter
The server's translation functionality is now complete. In the next chapter, we use cpp-httplib's client functionality to add the ability to fetch and manage models from Hugging Face.
**Next:** [Adding Model Download and Management](../ch04-model-management)
By the end of Chapter 3, the server's translation functionality was fully in place. However, the only model file available is the one we manually downloaded in Chapter 1. In this chapter, we'll use cpp-httplib's **client functionality** to enable downloading and switching Hugging Face models from within the app.
Once complete, you'll be able to manage models with requests like these:
# Select a different model (automatically downloads if not yet available)
curl -N -X POST http://localhost:8080/models/select \
-H "Content-Type: application/json" \
-d '{"model": "gemma-2-9b-it"}'
```
```text
data: {"status":"downloading","progress":0}
data: {"status":"downloading","progress":12}
...
data: {"status":"downloading","progress":100}
data: {"status":"loading"}
data: {"status":"ready"}
```
## 4.1 httplib::Client Basics
So far we've only used `httplib::Server`, but cpp-httplib also provides client functionality. Since Hugging Face uses HTTPS, we need a TLS-capable client.
```cpp
#include <httplib.h>
// Including the URL scheme automatically uses SSLClient
httplib::Client cli("https://huggingface.co");
// Automatically follow redirects (Hugging Face redirects to a CDN)
cli.set_follow_location(true);
auto res = cli.Get("/api/models");
if (res && res->status == 200) {
std::cout << res->body << std::endl;
}
```
To use HTTPS, you need to enable OpenSSL at build time. Add the following to your `CMakeLists.txt`:
Defining `CPPHTTPLIB_OPENSSL_SUPPORT` enables `httplib::Client("https://...")` to make TLS connections. On macOS, you also need to link the CoreFoundation and Security frameworks to access the system certificate store. See Section 4.8 for the complete `CMakeLists.txt`.
## 4.2 Defining the Model List
Let's define the list of models that the app can handle. Here are four models we've verified for translation tasks.
Up through Chapter 3, we stored models in the `models/` directory within the project. However, when managing multiple models, a dedicated app directory makes more sense. On macOS/Linux we use `~/.translate-app/models/`, and on Windows we use `%APPDATA%\translate-app\models\`.
```cpp
std::filesystem::path get_models_dir() {
#ifdef _WIN32
auto env = std::getenv("APPDATA");
auto base = env ? std::filesystem::path(env) : std::filesystem::path(".");
return base / "translate-app" / "models";
#else
auto env = std::getenv("HOME");
auto base = env ? std::filesystem::path(env) : std::filesystem::path(".");
return base / ".translate-app" / "models";
#endif
}
```
If the environment variable isn't set, it falls back to the current directory. The app creates this directory at startup (`create_directories` won't error even if it already exists).
## 4.4 Rewriting Model Initialization
We rewrite the model initialization at the beginning of `main()`. In Chapter 1 we hardcoded the path, but from here on we support model switching. We track the currently loaded filename in `selected_model` and load the first entry in `MODELS` at startup. The `GET /models` and `POST /models/select` handlers reference and update this variable.
Since cpp-httplib runs handlers concurrently on a thread pool, reassigning `llm` while another thread is calling `llm.chat()` would crash. We add a `std::mutex` to protect against this.
```cpp
int main() {
auto models_dir = get_models_dir();
std::filesystem::create_directories(models_dir);
std::string selected_model = MODELS[0].filename;
auto path = models_dir / selected_model;
// Automatically download the default model if not yet present
std::cerr << "\nFailed to download model." << std::endl;
return 1;
}
std::cout << std::endl;
}
auto llm = llamalib::Llama{path};
std::mutex llm_mutex; // Protect access during model switching
// ...
}
```
This ensures that users don't need to manually download models with curl on first launch. It uses the `download_model` function from Section 4.6 and displays progress on the console.
## 4.5 The `GET /models` Handler
This returns the model list with information about whether each model has been downloaded and whether it's currently selected.
GGUF models are several gigabytes, so we can't load the entire file into memory. By passing callbacks to `httplib::Client::Get`, we can receive data chunk by chunk.
```cpp
// content_receiver: callback that receives data chunks
- We send SSE events directly from the `download_model` progress callback. This is an application of `set_chunked_content_provider` + `sink.os` from Chapter 3
- Since the callback returns `sink.os.good()`, the download stops if the client disconnects. The cancel button we add in Chapter 5 uses this
- When we update `selected_model`, it's reflected in the `selected` flag of `GET /models`
- The `llm` reassignment is protected by `llm_mutex`. The `/translate` and `/translate/stream` handlers also lock the same mutex, so inference can't run during a model switch (see the complete code)
## 4.8 Complete Code
Here is the complete code with model management added to the Chapter 3 code.
// Allow the server to be stopped with `Ctrl+C` (`SIGINT`) or `kill` (`SIGTERM`)
signal(SIGINT, signal_handler);
signal(SIGTERM, signal_handler);
std::cout << "Listening on http://127.0.0.1:8080" << std::endl;
svr.listen("127.0.0.1", 8080);
}
```
</details>
## 4.9 Testing
Since we added OpenSSL configuration to CMakeLists.txt, we need to re-run CMake before building.
```bash
cmake -B build
cmake --build build -j
./build/translate-server
```
### Checking the Model List
```bash
curl http://localhost:8080/models
```
The gemma-2-2b-it model downloaded in Chapter 1 should show `downloaded: true` and `selected: true`.
### Switching to a Different Model
```bash
curl -N -X POST http://localhost:8080/models/select \
-H "Content-Type: application/json" \
-d '{"model": "gemma-2-9b-it"}'
```
Download progress streams via SSE, and `"ready"` appears when it's done.
### Comparing Translations Across Models
Let's translate the same sentence with different models.
```bash
# Translate with gemma-2-9b-it (the model we just switched to)
curl -X POST http://localhost:8080/translate \
-H "Content-Type: application/json" \
-d '{"text": "The quick brown fox jumps over the lazy dog.", "target_lang": "ja"}'
# Switch back to gemma-2-2b-it
curl -N -X POST http://localhost:8080/models/select \
-H "Content-Type: application/json" \
-d '{"model": "gemma-2-2b-it"}'
# Translate the same sentence
curl -X POST http://localhost:8080/translate \
-H "Content-Type: application/json" \
-d '{"text": "The quick brown fox jumps over the lazy dog.", "target_lang": "ja"}'
```
Translation results vary depending on the model, even with the same code and the same prompt. Since cpp-llamalib automatically applies the appropriate chat template for each model, no code changes are needed.
## Next Chapter
The server's main features are now complete: REST API, SSE streaming, and model download and switching. In the next chapter, we'll add static file serving and build a Web UI you can use from a browser.
title: "6. Turning It into a Desktop App with WebView"
order: 6
---
In Chapter 5, we completed a translation app you can use from a browser. But every time, you have to start the server, open the URL in a browser... Wouldn't it be nice to just double-click and start using it, like a normal app?
In this chapter, we'll do two things:
1. **WebView integration** — Use [webview/webview](https://github.com/webview/webview) to turn it into a desktop app that runs without a browser
2. **Single binary packaging** — Use [cpp-embedlib](https://github.com/yhirose/cpp-embedlib) to embed HTML/CSS/JS into the binary, making the distributable a single file
When finished, you'll be able to just run `./translate-app` to open a window and start translating.
The model downloads automatically on first launch, so the only thing you need to give users is the single binary.
## 6.1 Introducing webview/webview
[webview/webview](https://github.com/webview/webview) is a library that lets you use the OS's native WebView component (WKWebView on macOS, WebKitGTK on Linux, WebView2 on Windows) from C/C++. Unlike Electron, it doesn't bundle its own browser, so the impact on binary size is negligible.
We'll fetch it with CMake. Add the following to your `CMakeLists.txt`:
```cmake
# webview/webview
FetchContent_Declare(webview
GIT_REPOSITORY https://github.com/webview/webview
GIT_TAG master
)
FetchContent_MakeAvailable(webview)
```
This makes the `webview::core` CMake target available. When you link it with `target_link_libraries`, it automatically sets up include paths and platform-specific frameworks.
> **macOS**: No additional dependencies are needed. WKWebView is built into the system.
>
> **Linux**: WebKitGTK is required. Install it with `sudo apt install libwebkit2gtk-4.1-dev`.
>
> **Windows**: The WebView2 runtime is required. It comes pre-installed on Windows 11. For Windows 10, download it from the [official Microsoft website](https://developer.microsoft.com/en-us/microsoft-edge/webview2/).
## 6.2 Running the Server on a Background Thread
Up through Chapter 5, the server's `listen()` was blocking the main thread. To use WebView, we need to run the server on a separate thread and run the WebView event loop on the main thread.
```cpp
#include "webview/webview.h"
#include <thread>
int main() {
// ... (server setup is the same as Chapter 5) ...
- **`bind_to_any_port`** — Instead of `listen("127.0.0.1", 8080)`, we let the OS choose an available port. Since desktop apps can be launched multiple times, using a fixed port would cause conflicts
- **`listen_after_bind`** — Starts accepting requests on the port reserved by `bind_to_any_port`. While `listen()` does bind and listen in one call, we need to know the port number first, so we split the operations
- **Shutdown order** — When the WebView window is closed, we stop the server with `svr.stop()` and wait for the thread to finish with `server_thread.join()`. If we reversed the order, WebView would lose access to the server
The `signal_handler` from Chapter 5 is no longer needed. In a desktop app, closing the window means terminating the application.
## 6.3 Embedding Static Files with cpp-embedlib
In Chapter 5, we served files from the `public/` directory, so you'd need to distribute `public/` alongside the binary. With [cpp-embedlib](https://github.com/yhirose/cpp-embedlib), you can embed HTML, CSS, and JavaScript into the binary, packaging the distributable into a single file.
`cpp_embedlib_add` converts the files under `public/` into binary data at compile time and creates a static library called `WebAssets`. When linked, you can access the embedded files through a `Web::FS` object. `cpp-embedlib-httplib` is a helper library that provides the `httplib::mount()` function.
### Replacing set_mount_point with httplib::mount
Simply replace Chapter 5's `set_mount_point` with cpp-embedlib's `httplib::mount`:
```cpp
#include <cpp-embedlib-httplib.h>
#include "WebAssets.h"
// Chapter 5:
// svr.set_mount_point("/", "./public");
// Chapter 6:
httplib::mount(svr, Web::FS);
```
`httplib::mount` registers handlers that serve the files embedded in `Web::FS` over HTTP. MIME types are automatically determined from file extensions, so there's no need to manually set `Content-Type`.
The file contents are directly mapped to the binary's data segment, so no memory copies or heap allocations occur.
## 6.4 macOS: Adding the Edit Menu
If you try to paste text into the input field with `Cmd+V`, you'll find it doesn't work. On macOS, keyboard shortcuts like `Cmd+V` (paste) and `Cmd+C` (copy) are routed through the application's menu bar. Since webview/webview doesn't create one, these shortcuts never reach the WebView. We need to add a macOS Edit menu using the Objective-C runtime:
```cpp
#ifdef __APPLE__
#include <objc/objc-runtime.h>
void setup_macos_edit_menu() {
auto cls = [](const char *n) { return (id)objc_getClass(n); };
auto sel = sel_registerName;
auto msg = reinterpret_cast<id (*)(id, SEL)>(objc_msgSend);
auto msg_s = reinterpret_cast<id (*)(id, SEL, const char *)>(objc_msgSend);
auto msg_id = reinterpret_cast<id (*)(id, SEL, id)>(objc_msgSend);
auto msg_v = reinterpret_cast<void (*)(id, SEL, id)>(objc_msgSend);
auto msg_mi = reinterpret_cast<id (*)(id, SEL, id, SEL, id)>(objc_msgSend);
id mi = msg_mi(msg(cls("NSMenuItem"), sel("alloc")),
sel("initWithTitle:action:keyEquivalent:"),
str(title), sel(action), str(key));
msg_v(editMenu, sel("addItem:"), mi);
}
msg_v(editItem, sel("setSubmenu:"), editMenu);
msg_v(mainMenu, sel("addItem:"), editItem);
msg_v(app, sel("setMainMenu:"), mainMenu);
}
#endif
```
Call this before `w.run()`:
```cpp
#ifdef __APPLE__
setup_macos_edit_menu();
#endif
w.run();
```
On Windows and Linux, keyboard shortcuts are delivered directly to the focused control without going through the menu bar, so this workaround is macOS-specific.
Not a single line of handler code has changed. The REST API, SSE streaming, and model management built through Chapter 5 all work as-is.
## 6.6 Building and Testing
```bash
cmake -B build
cmake --build build -j
```
Launch the app:
```bash
./build/translate-app
```
No browser is needed. A window opens automatically. The same UI from Chapter 5 appears as-is, and translation and model switching all work just the same.
When you close the window, the server shuts down automatically. There's no need for `Ctrl+C`.
### What Needs to Be Distributed
You only need to distribute:
- The single `translate-app` binary
That's it. You don't need the `public/` directory. HTML, CSS, and JavaScript are embedded in the binary. Model files download automatically on first launch, so there's no need to ask users to prepare anything in advance.
## Next Chapter
Congratulations! 🎉
In Chapter 1, `/health` just returned `{"status":"ok"}`. Now we have a desktop app where you type text and translations stream in real time, pick a different model from a dropdown and it downloads automatically, and closing the window cleanly shuts everything down — all in a single distributable binary.
What we changed in this chapter was just the static file serving and the server startup. Not a single line of handler code changed. The REST API, SSE streaming, and model management we built through Chapter 5 all work as a desktop app, as-is.
In the next chapter, we'll shift perspective and read through the code of llama.cpp's own `llama-server`. Let's compare our simple server with a production-quality one and see what design decisions differ and why.
**Next:** [Reading the llama.cpp Server Source Code](../ch07-code-reading)
title: "7. Reading the llama.cpp Server Source Code"
order: 7
---
Over the course of six chapters, we built a translation desktop app from scratch. We have a working product, but it's ultimately a "learning-oriented" implementation. So how does "production-quality" code differ? Let's read the source code of `llama-server`, the official server bundled with llama.cpp, and compare.
`llama-server` is located at `llama.cpp/tools/server/`. It uses the same cpp-httplib, so you can read the code the same way as in the previous chapters.
## 7.1 Source Code Location
```ascii
llama.cpp/tools/server/
├── server.cpp # Main server implementation
├── httplib.h # cpp-httplib (bundled version)
└── ...
```
The code is contained in a single `server.cpp`. It runs to several thousand lines, but once you understand the structure, you can narrow down the parts worth reading.
## 7.2 OpenAI-Compatible API
The biggest difference between the server we built and `llama-server` is the API design.
**Our API:**
```text
POST /translate → {"translation": "..."}
POST /translate/stream → SSE: data: "token"
```
**llama-server's API:**
```text
POST /v1/chat/completions → OpenAI-compatible JSON
POST /v1/completions → OpenAI-compatible JSON
POST /v1/embeddings → Text embedding vectors
```
`llama-server` conforms to [OpenAI's API specification](https://platform.openai.com/docs/api-reference). This means OpenAI's official client libraries (such as the Python `openai` package) work out of the box.
```python
# Example of connecting to llama-server with the OpenAI client
Compatibility with existing tools and libraries is a big design decision. We designed a simple translation-specific API, but if you're building a general-purpose server, OpenAI compatibility has become the de facto standard.
## 7.3 Concurrent Request Handling
Our server processes requests one at a time. If another request arrives while a translation is in progress, it waits until the previous inference finishes. This is fine for a desktop app used by one person, but it becomes a problem for a server shared by multiple users.
`llama-server` handles concurrent requests through a mechanism called **slots**.
The key point is that tokens from each slot are not inferred **one by one in sequence**, but rather **all at once in a single batch**. GPUs excel at parallel processing, so processing two users simultaneously takes almost the same time as processing one. This is called "continuous batching."
In our server, cpp-httplib's thread pool assigns one thread per request, but the inference itself runs single-threaded inside `llm.chat()`. `llama-server` consolidates this inference step into a shared batch processing loop.
## 7.4 Differences in SSE Format
The streaming mechanism itself is the same (`set_chunked_content_provider` + SSE), but the data format differs.
Our format simply sends the tokens. Because `llama-server` follows the OpenAI specification, even a single token comes wrapped in JSON. It may look verbose, but it includes useful information for clients, like an `id` to identify the request and a `finish_reason` to indicate why generation stopped.
## 7.5 KV Cache Reuse
In our server, we process the entire prompt from scratch on every request. Our translation app's prompt is short ("Translate the following text to ja..." + input text), so this isn't a problem.
`llama-server` reuses the KV cache for the prefix portion when a request shares a common prompt prefix with a previous request.
For chatbots that send a long system prompt and few-shot examples with every request, this alone dramatically reduces response time. The difference is night and day: processing several thousand tokens of system prompt every time versus reading them from cache in an instant.
For our translation app, where the system prompt is just a single sentence, the benefit is limited. However, it's an optimization worth keeping in mind when applying this to your own applications.
## 7.6 Structured Output
Since our translation API returns plain text, there was no need to constrain the output format. But what if you want the LLM to respond in JSON?
```text
Prompt: Analyze the sentiment of the following text and return it as JSON.
When you specify `json_schema`, tokens that don't conform to the grammar are excluded during token generation. This guarantees that the output is always valid JSON, so there's no need to worry about `json::parse` failing.
When embedding LLMs into applications, whether you can reliably parse the output directly impacts reliability. Grammar constraints are unnecessary for free-text output like translation, but they're essential for use cases where you need to return structured data as an API response.
## 7.7 Summary
Let's organize the differences we've covered.
| Aspect | Our Server | llama-server |
|------|-------------|--------------|
| API design | Translation-specific | OpenAI-compatible |
Our code is simple because of the assumption that "one person uses it as a desktop app." If you're building a server for multiple users or one that integrates with the existing ecosystem, `llama-server`'s design serves as a valuable reference.
Conversely, even 200 lines of code is enough to make a fully functional translation app. I hope this code reading exercise has also conveyed the value of "building only what you need."
## Next Chapter
In the next chapter, we'll cover the key points for swapping in your own library and customizing the app to make it truly yours.
**Next:** [Making It Your Own](../ch08-customization)
Through Chapter 7, we've built a translation desktop app and studied how production-quality code differs. In this chapter, let's go over the key points for **turning this app into something entirely your own**.
The translation app was just a vehicle. Replace llama.cpp with your own library, and the same architecture works for any application.
## 8.1 Swapping Out the Build Configuration
First, replace the llama.cpp-related `FetchContent` entries in `CMakeLists.txt` with your own library.
```cmake
# Remove: llama.cpp and cpp-llamalib FetchContent
# Add: your own library
FetchContent_Declare(my_lib
GIT_REPOSITORY https://github.com/yourname/my-lib
GIT_TAG main
)
FetchContent_MakeAvailable(my_lib)
target_link_libraries(my-app PRIVATE
httplib::httplib
nlohmann_json::nlohmann_json
my_lib # Your library instead of cpp-llamalib
# ...
)
```
If your library doesn't support CMake, you can place the header and source files directly in `src/` and add them to `add_executable`. Keep cpp-httplib, nlohmann/json, and webview as they are.
## 8.2 Adapting the API to Your Task
Change the translation API's endpoints and parameters to match your task.
| Translation app | Your app (e.g., image processing) |
The same goes for SSE streaming. If your library has a function that reports progress via a callback, you can use the exact same pattern from Chapter 3 to send incremental responses. SSE isn't limited to LLMs — it's useful for any time-consuming task: image processing progress, data conversion steps, long-running computations.
## 8.3 Design Considerations
### Libraries with Expensive Initialization
In this book, we load the LLM model at the top of `main()` and keep it in a variable. This is intentional. Loading the model on every request would take several seconds, so we load it once at startup and reuse it. If your library has expensive initialization (loading large data files, acquiring GPU resources, etc.), the same approach works well.
### Thread Safety
cpp-httplib processes requests concurrently using a thread pool. In Chapter 4 we protected the `llm` object with a `std::mutex` to prevent crashes during model switching. The same pattern applies when integrating your own library. If your library isn't thread-safe or you need to swap objects at runtime, protect access with a `std::mutex`.
## 8.4 Customizing the UI
Edit the three files in `public/`.
- **`index.html`** — Change the input form layout. Swap `<textarea>` for `<input type="file">`, add parameter fields, etc.
- **`style.css`** — Adjust the layout and colors. Keep the two-column design or switch to a single column
- **`script.js`** — Update the `fetch()` target URLs, request bodies, and how responses are displayed
Even without changing any server code, just swapping the HTML makes the app look completely different. Since these are static files, you can iterate quickly — just reload the browser without restarting the server.
This book used plain HTML, CSS, and JavaScript, but combining them with a frontend framework like Vue or React, or a CSS framework, would let you build an even more polished app.
## 8.5 Distribution Considerations
### Licenses
Check the licenses of the libraries you're using. cpp-httplib (MIT), nlohmann/json (MIT), and webview (MIT) all allow commercial use. Don't forget to check the license of your own library and its dependencies too.
### Models and Data Files
The download mechanism we built in Chapter 4 isn't limited to LLM models. If your app needs large data files, the same pattern lets you auto-download them on first launch, keeping the binary small while sparing users the manual setup.
If the data is small, you can embed it directly into the binary with cpp-embedlib.
### Cross-Platform Builds
webview supports macOS, Linux, and Windows. When building for each platform:
- **macOS** — No additional dependencies
- **Linux** — Requires `libwebkit2gtk-4.1-dev`
- **Windows** — Requires the WebView2 runtime (pre-installed on Windows 11)
Consider setting up cross-platform builds in CI (e.g., GitHub Actions) too.
## Closing
Thank you so much for reading to the end. 🙏
This book started with `/health` returning `{"status":"ok"}` in Chapter 1. From there we built a REST API, added SSE streaming, downloaded models from Hugging Face, created a browser-based Web UI, and packaged it all into a single-binary desktop app. In Chapter 7 we read through `llama-server`'s code and learned how production-quality servers differ in their design. It's been quite a journey, and I'm truly grateful you stuck with it all the way through.
Looking back, we used several key cpp-httplib features hands-on:
- **Server**: routing, JSON responses, SSE streaming with `set_chunked_content_provider`, static file serving with `set_mount_point`
- **Client**: HTTPS connections, redirect following, large downloads with content receivers, progress callbacks
- **WebView integration**: `bind_to_any_port` + `listen_after_bind` for background threading
cpp-httplib offers many more features beyond what we covered here, including multipart file uploads, authentication, timeout control, compression, and range requests. See [A Tour of cpp-httplib](../../tour/) for details.
These patterns aren't limited to a translation app. If you want to add a web API to your C++ library, give it a browser UI, or ship it as an easy-to-distribute desktop app — I hope this book serves as a useful reference.
Take your own library, build your own app, and have fun with it. Happy hacking! 🚀
title: "Building a Desktop LLM App with cpp-httplib"
order: 0
---
Have you ever wanted to add a web API to your own C++ library, or quickly build an Electron-like desktop app? In Rust you might reach for "Tauri + axum," but in C++ it always seemed out of reach.
With [cpp-httplib](https://github.com/yhirose/cpp-httplib), [webview/webview](https://github.com/webview/webview), and [cpp-embedlib](https://github.com/yhirose/cpp-embedlib), you can take the same approach in pure C++ — and produce a small, easy-to-distribute single binary.
In this tutorial we build an LLM-powered translation app using [llama.cpp](https://github.com/ggml-org/llama.cpp), progressing step by step from "REST API" to "SSE streaming" to "Web UI" to "desktop app." Translation is just the vehicle — replace llama.cpp with your own library and the same architecture works for any application.
If you know basic C++17 and understand the basics of HTTP / REST APIs, you're ready to start.
## Chapters
1. **[Set up the project](ch01-setup)** — Fetch dependencies, configure the build, write scaffold code
2. **[Embed llama.cpp and create a REST API](ch02-rest-api)** — Return translation results as JSON
3. **[Add token streaming with SSE](ch03-sse-streaming)** — Stream responses token by token
4. **[Add model discovery and management](ch04-model-management)** — Download and switch models from Hugging Face
5. **[Add a Web UI](ch05-web-ui)** — A browser-based translation interface
6. **[Turn it into a desktop app with WebView](ch06-desktop-app)** — A single-binary desktop application
7. **[Reading the llama.cpp server source code](ch07-code-reading)** — Compare with production-quality code
8. **[Making it your own](ch08-customization)** — Swap in your own library and customize
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