oSIP is an implementation of SIP. This library aims to provide
multimedia and telecom software developers an easy and powerful
interface to initiate and control SIP based sessions in their
applications. oSIP is little in size and code and thus could be
used to implement IP soft-phone as well as embedded SIP
software. oSIP does not intend to provide a high layer API for
controlling "SIP Session" at this step. Instead, it currently
provides an API for the SIP message parser, SDP message parser,
and library to handle "SIP transactions."