How to know sending result? suceess or failure

```

How to know sending result? suceess or failure.

客户端在连接成功后，又关闭了浏览器，这时发送给该客户��
�的消息肯定不成功，怎么判断发送不成功，以便进行记录，�
��次再重复给客户端发送该消息。
```

Original issue reported on code.google.com by `wang.zh...@gmail.com` on 14 Nov 2014 at 7:59
