期刊文章，主要介绍SIP协议，以及用JAVA 接口实现用户代理软件的方法-Journal articles, mainly introduces the SIP protocol, as well as the method of using JAVA interface to realize the user agent software

java 文件，isp protocol 电话，里面有client的部分，需要添加server-java files ， sip phone ，there are client，but we need you completed this project