private void onMessage(object sender, MessageEventArgs e)
 {
     Log.Trace("onMessage: " + e.Data);
     if (e.IsText)
     {
         var command   = CommandBase.FromJson(e.Data);
         var receivers = OnRequest.GetInvocationList();
         foreach (EventHandler <CommandBase> receiver in receivers)
         {
             OnRequest?.BeginInvoke(this, command, null, null);
         }
     }
 }