Fix Host header in websocket examples

closes #1633

example/websocket/client/sync/websocket_client_sync.cpp

@@ -43,9 +43,9 @@ int main(int argc, char** argv)
                 "    websocket-client-sync echo.websocket.org 80 \"Hello, world!\"\n";
             return EXIT_FAILURE;
         }
-        auto const host = argv[1];
-        auto const port = argv[2];
-        auto const text = argv[3];
+        std::string host = argv[1];
+        auto const  port = argv[2];
+        auto const  text = argv[3];
 
         // The io_context is required for all I/O
         net::io_context ioc;
@@ -58,7 +58,12 @@ int main(int argc, char** argv)
         auto const results = resolver.resolve(host, port);
 
         // Make the connection on the IP address we get from a lookup
-        net::connect(ws.next_layer(), results.begin(), results.end());
+        auto ep = net::connect(ws.next_layer(), results);
+
+        // Update the host_ string. This will provide the value of the
+        // Host HTTP header during the WebSocket handshake.
+        // See https://tools.ietf.org/html/rfc7230#section-5.4
+        host += ':' + std::to_string(ep.port());
 
         // Set a decorator to change the User-Agent of the handshake
         ws.set_option(websocket::stream_base::decorator(