     {
       if (connection_open) return;
 
       cout << "Server start listening on port "<< port << endl;
       communicator=vtkSmartPointer<Communicator>::New();
       communicator->server_listen_num_retry=1;
       communicator->server_listen_waiting_time=1000*wtime;
       int rc=communicator->ServerConnect(port);
       if (rc)  
         cout << "Server connected" << endl;
       else
       {
         cout << "Nobody is listening ... giving up" << endl;
         throw std::runtime_error("Server connection failed");
         exit(1);
       }
       connection_open=true;
     }