A Node process can answer and dial PeerJS browser peers with node-datachannel and the PeerServer protocol written by hand

Fact

A server can be a PeerJS data peer without the PeerJS client or a browser: open the PeerServer WebSocket itself and answer offers with node-datachannel, which ships prebuilt binaries as per-platform optional dependencies (no compiler, no install script). Browsers using PeerJS 1.5 cannot tell it apart from another browser, and Chrome's default mDNS-hidden host candidates still connect.

Why it matters

It lets an always-on machine (a home server, a bot, a store-and-forward service) join a peer-to-peer app under a fixed id, with no open ports, tunnel or HTTPS certificate, reusing the app's signaling and TURN servers.

How to apply

• Connect wss://host:port/<path>peerjs?key=peerjs&id=<id>&token=<random> (the cloud is 0.peerjs.com:443, path /). Send {"type":"HEARTBEAT"} every 5 s. OPEN means registered; ID-TAKEN means try again later.

• A dial arrives as OFFER with src and payload: { sdp: { type, sdp }, type: "data", connectionId, label, serialization, reliable }. Create new PeerConnection(connectionId, { iceServers }), call setRemoteDescription(payload.sdp.sdp, "offer"), and send what the callbacks produce, with dst: src:

  • onLocalDescription(sdp, type) → ANSWER, payload: { sdp: { type, sdp }, type: "data", connectionId }
  • onLocalCandidate(candidate, mid) → CANDIDATE, payload: { candidate: { candidate, sdpMid: mid, sdpMLineIndex: 0 }, type: "data", connectionId }
• Feed incoming CANDIDATE payloads to addRemoteCandidate(c.candidate, c.sdpMid). The browser opened the channel; it arrives in onDataChannel.
• To dial a browser instead, register under any random id, then createDataChannel(connectionId) (making the channel starts the offer) and send onLocalDescription as OFFER, payload: { sdp: { type, sdp }, type: "data", connectionId, label: connectionId, serialization: "raw", reliable: true }. The browser's peer.on('connection') fires as for any PeerJS caller; its ANSWER goes to setRemoteDescription(sdp.sdp, "answer"), and EXPIRE means nobody holds that id.
• With serialization: "raw" the channel carries the page's strings as they are; chunk long ones yourself, as in the browser.