https://www.hongweipeng.com/index.php/archives/835/
http://www.cnblogs.com/lingyunhu/p/rtc28.html
https://jitsi.org/Projects/JitsiVideobridge
https://www.youtube.com/watch?v=OT6kwzsQeVc&feature=youtu.be
https://my.oschina.net/langhuihui/blog/598338
https://my.oschina.net/langhuihui/blog/602265
https://my.oschina.net/langhuihui/blog/612144