通过代码示例，演示如果使用windows API 设置TCP/IP心跳包，利用TCP/IP协议自带的KeepAlive功能断开孤立连接。

网络编程之TCP的保活定时器Network Programming TCP s keep-alive timer -Network Programming TCP-Keepalive Timer Network Programming TCP' s keep-alive timer

设置好keepalive以后，我们通过实验来看看当client异常退出或是网络断掉的情况下，keepalive怎么通知我们异常断开的情况。这里采用select模式，实验环境为XP系统和Win7系统，几种情况返回值如下： 1． 正常断开 select函数正常返回，recv函数返回0 2． 异常断开 -Set keepalive after the experiment to look at client quit unexpectedly or network brok