JsSIP uses the SIP over WebSocket transport for sending an receiving SIP requests and responses, and thus, it requires a SIP proxy/server with WebSocket support. Currently the following SIP servers have been tested:
WebRTC Web browsers
At media plane (audio calls), JsSIP version 0.2.0 works with Chrome browser from version 24.
At signaling plane (SIP protocol), JsSIP runs in any WebSocket capable browser. Here a list of WebSocket support in Web browsers.