Connection to servers does not block the process anymore

src/irc/irc_client.hpp

@@ -29,6 +29,10 @@ public:
    * Connect to the IRC server
    */
   void start();
+  /**
+   * Called when the connection to the server cannot be established
+   */
+  void on_connection_failed(const std::string& reason) override final;
   /**
    * Called when successfully connected to the server
    */