SIP for WebRTC has been notably implemented in theJsSIP JavaScript Open Source library. JsSIP was written by José Luis Millán, Iñaki Baz Castillo, and Saúl Ibarra Corretgé aka the Basque VoIP Mafia, also co-authors of RFC 7118 that defines the use of WS and WSS for SIP:

JsSIP was then forked and further developed by Will Mitchell and its team, while working at OnSIP. The result as been released as open source SIP.js library. SIP.js as of today has widespread adoption, and is the most used Javascript WebRTC SIP library in FreeSWITCH Community:

Another notable and independent (actually, the first SIP client for HTML5) opensource SIP library implementation in JavaScript is sipml5, developed by Doubango Telecom.

Each one of these libraries is readily available on the Internet, with full documentation, example clients, etc. The most actively developed and supported seems to be SIP.js. We'll look at SIP.js in action later in this chapter, implementing the WebRTC Rooms application.