根据WinSock的编程原理，采用流套接字编程，运用面向对象的方法分析了SIP协议，详细地描述了用C++语言实现SIP协议的呼叫建立过程。-under WinSock programming theory, flow socket programming, use of the object-oriented method for the SIP, detailed descr iption of C language of the SIP call setup process.