https://docs.oracle.com/javaee/7/tutorial/doc/websocket.htm

http://blog.csdn.net/chifengxin/article/details/14521093

https://www.ibm.com/developerworks/cn/web/1112_huangxa_websocket/

如何理解 TCP/IP, SPDY, WebSocket 三者之间的关系?

http://www.zhihu.com/question/20097129