说明：  jssip 一个基于webrtc的web sip电话功能。可以连接websocket
(JsSIP: The JavaScript SIP Library Runs in the browser and Node.js SIP over WebSocket (use real SIP in your web apps) Audio/video calls (WebRTC) and instant messaging Lightweight! 100 pure JavaScript built the ground up Easy to use and powerful user API Works with OverSIP, Kamailio, Asterisk, OfficeSIP and more (more info) Written by the authors of RFC 7118 and OverSIP )