Introduction - If you have any usage issues, please Google them yourself
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