This allows connecting between clients without using external servers, which is useful to OEMs if they are working in a network without internet connection. Implementation uses custom AppRTCClient that replaces WebSocketRTCClient if roomId looks like an IP. Instead of a web socket, this class uses direct TCP connection between peers as a signaling channel.
Review-Url: https://codereview.webrtc.org/1963053002
Cr-Commit-Position: refs/heads/master@{#12789}
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