WebRTC：网页实时交流
WebRTC (Web Real-Time Communication) is a free and open-source project providing web browsers and mobile applications with real-time communication (RTC) via application programming interfaces (APIs). It allows audio and video communication to work inside web pages by allowing direct peer-to-peer communication, eliminating the need to install plugins or download native apps. Supported by Apple, Google, Microsoft, Mozilla, and Opera, WebRTC specifications have been published by the World Wide Web Consortium (W3C) and the Internet Engineering Task Force (IETF).

RTCIceCandidate：

First time to implement webrtc? Having trouble with signal server? Struggling to figure out what actually is going on with webrtc? Or you are just curious how I managed to build a webrtc server with Ruby on Rails. Then this is the place, keep reading!
第一次使用（实现）webrtc？
这里用implement ,而不是use， 翻译成中文都可以为“用”的意思，但是implement偏向于把理论去实践的‘实践‘，有因果在里面，好比中文的知易行难中的"行" ，可以翻译为“实现”，而use也就仅仅是use，随便use，几乎和中文的’用‘一模一样了。这里还有个practise动词/practice名词也是类似的意思，但它强调的是反复的做。You should practice playing piano every day.。

搞不清楚signal服务器？ 
signal  [ˈsɪɡnəl] 信号和single 有点像，一不小心就看岔了。

还不明白webrtc到底咋么用？

或者你好奇我是怎么通过ruby on rails建立webrtc 服务器。那就继续往下看。

First of all. Let’s forget about detail code implementation, let’s discuss the theory behind the webrtc and see why they are not that difficult actually.
首先，不要去想实现webrtc的细节，先看看webrtc背后的原理，你就会明白这也没那么难。

第一个问题： 我要干什么？
你要去talk to another person on the internet.
第二个问题： 告诉我你在哪？
你告诉我你在哪，我告诉你我在哪。需要一个我们都信任的服务器来传递。 这个就是 signaling server.
第三个问题：你不清楚你的互联网IP地址，怎么办？
iceServer来帮忙，iceServer可以找到你的真实IP地址。并且得到链接彼此的方法，发送信息给对方。


https://medium.com/@BranLiang/a-complete-guide-to-webrtc-with-ruby-on-rails-9ea68e67154e