WebRTC (P2P): пример кода

// The Perfect Negotiation shape — offer/answer over YOUR signaling channel.
const pc = new RTCPeerConnection({
  iceServers: [
    { urls: 'stun:stun.l.google.com:19302' },              // find public address
    { urls: 'turn:turn.example.com', username: 'u', credential: 'p' }, // relay fallback
  ],
});

// 1. Send our ICE candidates to the other peer as they're discovered.
pc.onicecandidate = ({ candidate }) => candidate && signal.send({ candidate });

// 2. A reliable data channel (no server on the hot path).
const chan = pc.createDataChannel('chat');
chan.onmessage = (e) => render(e.data);

// 3. Caller creates the offer; callee answers. Both go over signaling.
const offer = await pc.createOffer();
await pc.setLocalDescription(offer);
signal.send({ sdp: pc.localDescription });

// 4. On the other side, on receiving the offer:
async function onSignal({ sdp, candidate }) {
  if (sdp) {
    await pc.setRemoteDescription(sdp);
    if (sdp.type === 'offer') {
      await pc.setLocalDescription(await pc.createAnswer());
      signal.send({ sdp: pc.localDescription });
    }
  } else if (candidate) {
    await pc.addIceCandidate(candidate); // may arrive before/after the SDP
  }
}