development files for the SIP library libosip2 header files and static libraries to assist in development of programs wishing to use SIP. The oSIP library is written in C, is thread safe and has no dependencies except the standard C library. oSIP could be used to implement an IP soft-phone as well as embedded SIP software. oSIP is not limited to endpoint agents implementations and can also be used to implement SIP proxies or registration services. oSIP currently provides an API for the SIP message parser, SDP message parser, and library to handle "SIP transactions" as defined by the SIP standards (RFC3261).