Sippet

A C++ library designed to be a Chrome SIP stack.

Current status: Work-in-progress

Sippet is an open-source SIP User-Agent library, compliant with the IETF RFC 3261 specification. It can be used as a building block for SIP client software for uses such as VoIP, IM, and many other real-time and P2P communication services.

The main target was to enable Javascript applications to use UDP, TCP and TLS transports along WebSocket. Existing SIP solutions for the browser are forced to use the WebSockets API to send/receive SIP messages. But for many service providers, the WebSocket protocol could not be a feasible solution due to scalability, support and other business constraints.

By the way, the stack can be used as a full client-side C++ Stack (full-featured) without Javascript integration.

Features

• Support to symmetric response routing (RFC 3581).
• Support to client-initiated connections (RFC 5626).
• Multiplatform: same platforms supported by Chromium.
• Parsing of SIP and Tel URIs, compatible with GURL.
• TODO: Websockets, just in case.
• SOCKS for stream-oriented connections, inherited from system settings.
• Pass-through HTTP proxies using CONNECT (SIP over HTTP proxies).
• Flexible SSL/TLS support (client-side certificates, restrict or relaxed cipher list).

Fun stuff

• Added G.729 support to WebRTC: use at your own risk, you have to pay royalties if you want to use this codec commercially.
  • The source code is now based on ITU-T release of October 2006, and include some optimizations provided by the WebRTC signal processing library. Several optimizations available in other source codes (such as CSipSimple and Siphon) were discarded as they don't consider saturation. Precision was considered more important than optimization in this derived work.
• Created a 'compatibility mode' for WebRTC, so it can negotiate media without supporting SRTP/DTLS and ICE.