code: protected void flushQueuedMessages(IoSession session, AttachedSessionManager attachedSessionManager) {
          Queue<Object> messageQueue = getMessageQueue(session);
          if (messageQueue != null) {
              flushQueuedMessages(messageQueue, session, attachedSessionManager);
              // Note: leave messageQueue intact on session to avoid race condition
              // will be cleared by next received message anyway
          }
      }
docs: called by connect listener in proxy service handler