使用websocket进行消息推送服务

Websocket主要做消息推送，简单，轻巧，比comet好用

入门了解：https://www.cnblogs.com/xdp-gacl/p/5193279.html

/**
 * A Web Socket session represents a conversation between two web socket endpoints. As soon
 * as the websocket handshake completes successfully, the web socket implementation provides
 * the endpoint an open websocket session. The endpoint can then register interest in incoming
 * messages that are part of this newly created session by providing a MessageHandler to the
 * session, and can send messages to the other end of the conversation by means of the RemoteEndpoint object
 * obtained from this session.
 */