SIP协议是一个用于建立，更改和终止多媒体会话的应用层控制协议。它是IETF多媒体数据和控制体系结构的一部分并大量借鉴了成熟的HTTP协议，具有易扩展、易实现等特点，因此非常适合用于实现基于因特网的多媒体会议、IP电话等系统。本系统使用Java实现了一个简单的VOIP电话应用系统。-SIP is a protocol for the establishment, modification and termination of multi-media session control protocol application layer. It is the IETF multimedia data and control architecture and a large number of reference as part of the HTTP protocol a mature, easy expansion, easy to achieve such characteristics, it is very suitable for the realization of Internet-based multimedia conferencing, IP phones and other systems. The system uses Java to achieve a simple VOIP phone applications.