(websocket server) Handle programmer error when the server callback is not registered properly (fix #227)

ixwebsocket/IXWebSocket.cpp

@@ -405,6 +405,11 @@ namespace ix
         _onMessageCallback = callback;
     }
 
+    bool WebSocket::isOnMessageCallbackRegistered() const
+    {
+        return _onMessageCallback != nullptr;
+    }
+
     void WebSocket::setTrafficTrackerCallback(const OnTrafficTrackerCallback& callback)
     {
         _onTrafficTrackerCallback = callback;

ixwebsocket/IXWebSocket.h

@@ -84,6 +84,7 @@ namespace ix
                    const std::string& reason = WebSocketCloseConstants::kNormalClosureMessage);
 
         void setOnMessageCallback(const OnMessageCallback& callback);
+        bool isOnMessageCallbackRegistered() const;
         static void setTrafficTrackerCallback(const OnTrafficTrackerCallback& callback);
         static void resetTrafficTrackerCallback();
 

ixwebsocket/IXWebSocketServer.cpp

@@ -86,6 +86,15 @@ namespace ix
         if (_onConnectionCallback)
         {
             _onConnectionCallback(webSocket, connectionState, std::move(connectionInfo));
+
+            if (!webSocket->isOnMessageCallbackRegistered())
+            {
+                logError("WebSocketServer Application developer error: Server callback improperly "
+                         "registerered.");
+                logError("Missing call to setOnMessageCallback inside setOnConnectionCallback.");
+                connectionState->setTerminated();
+                return;
+            }
         }
         else if (_onClientMessageCallback)
         {