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C++ SIP stack based on Chrome source code
...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.