I am working on an open source framework which connects nodes for collaboration and p2p transfer. I started off with WebRTC at the core but have since made it optional transport due to lack of portability. Snapdrop is amazing but if you give up on WebRTC you can use QR code for discovery and transfer files even when not on the same network.
Signalling through QR code or pen & paper while possible in theory is not feasible in practice because both sides need to exchange ICE candidates & offer/answer. So a signalling middleman, whether through websockets, SSE, polling, etc. is needed. And if you want to support network handoff then you need persistent connection to the signalling server for re-negotiation.
Yes, the first version is here: https://github.com/uhst/uhst-client-js and there is a demo Ping app: https://examples.run/ping/ . Originally my idea was to use SSE for signalling but in version 2 it becomes a relay between peers. This approach will make it portable to mobile (native, Flutter, RN) which is difficult to do with WebRTC. The added throughput and latency should be similar to using TURN server with WebRTC. Websockets are the more common choice for signalling but HTTP/2.0 brings a new life to SSE.
