TCP链接中主动断开链接netstat观察可能出现的状态流转是： ESTABLISHED->CLOSE_WAIT->TIME_WAIT->CLOSED ESTABLISHED->TIME_WAIT->CLOSE_WAIT->CLOSED ESTABLISHED->FIN_WAIT_1->FIN_WAIT_2->TIME_WAIT->CLOSED ESTABLISHED->FIN_WAIT_1->TIME_WAIT->CLOSED
中断连接端可以是client，也可以是server。
下图为client发起主动断开连接时，client和server的状态图。
详参：http://blog.csdn.net/whuslei/article/details/6667471
