http://blog.csdn.net/feiniu55662/article/details/16948639
https://www.baidu.com/baidu?tn=monline_3_dg&ie=utf-8&wd=Tcp%E4%B8%AD%E7%9A%84%E8%BF%9E%E6%8E%A5%E6%97%B6%E9%97%B4
https://zhidao.baidu.com/question/111291343.html
https://zhidao.baidu.com/question/691451568033778404.html?qbl=relate_question_1&word=Tcp%D6%D0%B5%C4%C1%AC%BD%D3%CA%B1%BC%E4
https://zhidao.baidu.com/question/583862906738530285.html?qbl=relate_question_0&word=Tcp%D6%D0%B5%C4%C1%AC%BD%D3%CA%B1%BC%E4
https://zhidao.baidu.com/question/570706838.html?qbl=relate_question_3&word=Tcp%D6%D0%B5%C4%C1%AC%BD%D3%CA%B1%BC%E4
https://www.baidu.com/baidu?tn=monline_3_dg&ie=utf-8&wd=socket%E4%B8%AD%E5%A6%82%E4%BD%95%E7%9F%A5%E9%81%93%E6%9C%8D%E5%8A%A1%E7%AB%AF%E5%9C%A8%E7%AD%89%E5%BE%85%E5%AE%A2%E6%88%B7%E7%AB%AF
长连接和保活 https://www.baidu.com/baidu?tn=monline_3_dg&ie=utf-8&wd=socket%E9%95%BF%E8%BF%9E%E6%8E%A5%E5%92%8C%E4%BF%9D%E6%B4%BB%E6%8A%80%E6%9C%AF
linux上查看socket的状态 https://www.baidu.com/baidu?tn=monline_3_dg&ie=utf-8&wd=linux%E4%B8%8A%E6%80%8E%E4%B9%88%E7%9C%8Bsocket%E7%9A%84%E7%8A%B6%E6%80%81
linux上查看进程状态 http://blog.csdn.net/u010164190/article/details/50907836
socket的正确关闭改良版 http://blog.csdn.net/chenlycly/article/details/41916061
Tcp连接的状态详解及故障排查 http://blog.csdn.net/hguisu/article/details/38700899
socket服务端如何关闭客户端的连接 http://bbs.csdn.net/topics/390955991/
socket死连接详解 http://blog.csdn.net/educast/article/details/7602325