RFC3261中文版，描述了SIP协议的基本概念，消息定义，各头字段说明。-Chinese version of RFC3261, SIP protocol describes the basic concepts, message definition, the header field notes.

该文档比较详细介绍了SIP协议的概念、报文解析、典型的呼叫流程以及应用场景。-The document more detailed introduces the concept of the SIP protocol, message parsing, the typical call process and application scenarios.

GBT28181协议测试码流，打印出测试中发送和接收端的SIP消息，供参考。-GBT28181 protocol test code flow, print out the test the sending and receiving the SIP message, for your reference.