Make it possible to set the user agent for websockets (microsoft#606)

* Make it possible to set the user agent for websockets

* Use headers() to communicate the user agent for websockets.

* Fix set_user_agent on Linux; use to_string_t.

Author: MathyV

Release/include/cpprest/ws_client.h

@@ -150,6 +150,12 @@ class websocket_client_config
         return m_sni_hostname;
     }
 
+    /// <summary>
+    /// Sets the User Agent to be used for the connection
+    /// </summary>
+    /// <param name="name">The User Agent to use, as a string.</param>
+    _ASYNCRTIMP void set_user_agent(const utf8string &user_agent);
+
     /// <summary>
     /// Gets the headers of the HTTP request message used in the WebSocket protocol handshake.
     /// </summary>

Release/src/websockets/client/ws_client_wspp.cpp

@@ -316,6 +316,15 @@ class wspp_callback_client : public websocket_client_callback_impl, public std::
             shutdown_wspp_impl<WebsocketConfigType>(con_hdl, false);
         });
 
+        // Set User Agent specified by the user. This needs to happen before any connection is created
+        const auto& headers = m_config.headers();
+
+        auto user_agent_it = headers.find(web::http::header_names::user_agent);
+        if (user_agent_it != headers.end())
+        {
+            client.set_user_agent(utility::conversions::to_utf8string(user_agent_it->second));
+        }
+
         // Get the connection handle to save for later, have to create temporary
         // because type erasure occurs with connection_hdl.
         websocketpp::lib::error_code ec;
@@ -327,7 +336,6 @@ class wspp_callback_client : public websocket_client_callback_impl, public std::
         }
 
         // Add any request headers specified by the user.
-        const auto & headers = m_config.headers();
         for (const auto & header : headers)
         {
             if (!utility::details::str_icmp(header.first, g_subProtocolHeader))

Release/src/websockets/client/ws_msg.cpp

@@ -28,6 +28,12 @@ namespace client
 {
 
 static ::utility::string_t g_subProtocolHeader = _XPLATSTR("Sec-WebSocket-Protocol");
+
+void websocket_client_config::set_user_agent(const utf8string &user_agent)
+{
+    headers().add(web::http::header_names::user_agent, utility::conversions::to_string_t(user_agent));
+}
+
 void websocket_client_config::add_subprotocol(const ::utility::string_t &name)
 {
     m_headers.add(g_subProtocolHeader, name);