linux操作系统下nat的简单实现代码，比内核源代码简单，容易看懂。-nat linux operating system, a simple implementation of the code than the kernel source code is simple, easy to understand.

STUN服务器代码，用于NAT穿越, 用于及时通讯，视频通话， 语音通话等穿透-stun server source code， use for NAT P2P application

pjsip项目源码包，能够实现voip，nat穿透等功能。-Pjsip project source code package, can achieve voip, NAT penetration, and other functions.