LIBSIP++ has evolved over years, has been used in a number of applications in our SIP-based test bed, and interoperates with a number of other standard compliant implementations such as Cisco IP phone, Pingtel IP phone and eStara software phone.

The library is designed for user agent type of applications such as stand-alone IP phone, conference server, answering machine, voice-mail, or telephony gateway. It provides user agent server and user agent client application programming interface (API), that can be used for basic call setup, instant messaging, presence, device control or other SIP-based applications. It does not implement the media codec or media transport.

The the C++ library API is based on event-driven callback architecture. It uses internal thread-pool to serve various protocol events and to optimize the use of system resources such as threads. The core architecture is shared with our SIP proxy and registration server.