jsr-180 (SIP) 实现源码。可以在真实手机上使用，但需要获得公网地址，只实现了UDP传输。只可研究学习，不可用于商业用途。-JSR-180 (SIP) to achieve source. In real phone use, but need public address, the only achieved UDP transmission. Learning can only study and may not be used for commercial purposes.