Check for WebRTC peers using the WebTorrent protocol (BitTorrent over WebRTC).
To see a demo visit this and try with this info hash: 6a9759bffd5c0af65319979fb7832189f4f3c35d
CheckWebPeer takes advantage of bittorrent-tracker's client and scrapes the (currently) 4 websocket trackers:
wss://tracker.openwebtorrent.com/
wss://tracker.webtorrent.io
wss://tracker.btorrent.xyz
wss://tracker.fastcast.nz
The client runs client-sided so it's not necessary to host it in a server, and it's pretty simple to understand as most of the code it's reused and adapted from bittorrent-tracker and instant.io.
MIT. Copyright (c) Joaquín Serna.