说明：  PJSIP是一个开源的SIP协议库，它实现了SIP、SDP、RTP、STUN、TURN和ICE。PJSIP作为基于SIP的一个多媒体通信框架提供了非常清晰的API，以及NAT穿越的功能。PJSIP具有非常好的移植性，几乎支持现今所有系统：从桌面系统、嵌入式系统到智能手机。　　 PJSIP同时支持语音、视频、状态呈现和即时通讯。PJSIP具有非常完善的文档，对开发者非常友好。　
(PJSIP is an open source SIP protocol library, which implements the SIP, SDP, RTP, STUN, TURN and ICE. PJSIP provided as a SIP-based multimedia communication framework very clear API, and NAT traversal function. PJSIP has a very good transplant, the system supports almost all of today: from desktop systems, embedded systems to smart phones. PJSIP supports voice, video, presence and instant messaging. PJSIP has a very well documented, the developer is very friendly.)