RTCPeerConnection

Signature

const pc = new RTCPeerConnection(configuration);
// configuration: { iceServers: [{ urls: 'stun:stun.l.google.com:19302' }] }

What it does

Represents a connection between the local browser and a remote peer. It negotiates session descriptions, gathers and applies ICE candidates, and carries media tracks and data channels once a route is established.

Key members

Member	Kind	Purpose
`createOffer()` / `createAnswer()`	method	Produce an SDP description to start or respond to negotiation.
`setLocalDescription()` / `setRemoteDescription()`	method	Apply the local or remote SDP.
`addIceCandidate()`	method	Add a candidate received from the remote peer.
`addTrack()` / `removeTrack()`	method	Attach or detach a media track.
`createDataChannel()`	method	Open an `RTCDataChannel` over the connection.
`connectionState`	property	Aggregate state: `new`, `connecting`, `connected`, `disconnected`, `failed`, `closed`.
`icecandidate`	event	Fires for each gathered local candidate; a null `candidate` marks the end.
`track`	event	Fires when a remote track is added.
`datachannel`	event	Fires when the remote peer opens a channel.

Behaviour & constraints

Negotiation is asymmetric: the offerer calls createOffer, the answerer calls createAnswer.
ICE candidates may arrive before or after the remote description; buffer early candidates if needed.
iceServers is optional but STUN is required to discover a public address behind NAT.
Setting a local description starts ICE gathering; icecandidate events follow.
Closing with close() is final: a new connection needs a new object.

Example

const pc = new RTCPeerConnection({
  iceServers: [{ urls: 'stun:stun.l.google.com:19302' }],
});

pc.onicecandidate = ({ candidate }) => {
  if (candidate) signalingSend({ candidate });
};

const offer = await pc.createOffer();
await pc.setLocalDescription(offer);
signalingSend({ sdp: pc.localDescription });