sip协议中英文版，详细介绍了SIP协议-sip protocol in English, detailing the SIP protocol

中国电信的SIP协议的技术规范（包括终端设备），通信类开发必备。-China Telecom SIP protocol specifications (including terminal equipment), communications development necessary.

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.