{{APIRef}}{{SeeCompatTable}}
The RTCPeerConnection interface represents a WebRTC connection between the local computer and a remote peer. It is used to handle efficient streaming of data between the two peers.
Note: RTCPeerConnection and {{domxref("RTCSessionDescription")}} are currently prefixed in most browsers, and the {{domxref("navigator.getUserMedia()")}} method is prefixed in many versions of some browsers; you should use code like the following to access these:
var peerConnection = window.RTCPeerConnection || window.mozRTCPeerConnection ||
window.webkitRTCPeerConnection || window.msRTCPeerConnection;
var sessionDescription = window.RTCSessionDescription || window.mozRTCSessionDescription ||
window.webkitRTCSessionDescription || window.msRTCSessionDescription;
navigator.getUserMedia = navigator.getUserMedia || navigator.mozGetUserMedia ||
navigator.webkitGetUserMedia || navigator.msGetUserMedia;
Simple code such as this is all it takes to ensure that your project will work on as many versions of as many browsers as possible.
Basic RTCPeerConnection usage involves negotiating a connection between your local machine and a remote one by generating Session Description Protocol to exchange between the two. The caller starts the process by sending an offer to the remote machine, which responds by either accepting or rejecting the call.
Both parties (the caller and the called party) need to set up their own RTCPeerConnection instances to represent their end of the peer-to-peer connection:
var pc = new RTCPeerConnection();
pc.onaddstream = function(obj) {
var vid = document.createElement("video");
document.appendChild(vid);
vid.srcObject = obj.stream;
}
// Helper functions
function endCall() {
var videos = document.getElementsByTagName("video");
for (var i = 0; i < videos.length; i++) {
videos[i].pause();
}
pc.close();
}
function error(err) {
endCall();
}
If you are the one initiating the call, you would use {{domxref("navigator.getUserMedia()")}} to get a video stream, then add the stream to the RTCPeerConnection. Once that's been done, call {{domxref("RTCPeerConnection.createOffer()")}} to create an offer, configure the offer, then send it to the server through which the connection is being mediated.
// Get a list of friends from a server
// User selects a friend to start a peer connection with
navigator.getUserMedia({video: true}, function(stream) {
// Adding a local stream won't trigger the onaddstream callback,
// so call it manually.
pc.onaddstream({stream: stream});
pc.addStream(stream);
pc.createOffer(function(offer) {
pc.setLocalDescription(new RTCSessionDescription(offer), function() {
// send the offer to a server to be forwarded to the friend you're calling.
}, error);
}, error);
});
On the opposite end, the friend will receive the offer from the server using whatever protocol is being used to do so. Once the offer arrives, {{domxref("navigator.getUserMedia()")}} is once again used to create the stream, which is added to the RTCPeerConnection. An {{domxref("RTCSessionDescription")}} object is created and set up as the remote description by calling {{domxref("RTCPeerConnection.setRemoteDescription()")}}.
Then an answer is created using {{domxref("RTCPeerConnection.createAnswer()")}} and sent back to the server, which forwards it to the caller.
var offer = getOfferFromFriend();
navigator.getUserMedia({video: true}, function(stream) {
pc.onaddstream({stream: stream});
pc.addStream(stream);
pc.setRemoteDescription(new RTCSessionDescription(offer), function() {
pc.createAnswer(function(answer) {
pc.setLocalDescription(new RTCSessionDescription(answer), function() {
// send the answer to a server to be forwarded back to the caller (you)
}, error);
}, error);
}, error);
});
Back on the original machine, the response is received. Once that happens, call {{domxref("RTCPeerConnection.setRemoteDescription()")}} to set the response as the remote end of the connection.
// pc was set up earlier when we made the original offer var offer = getResponseFromFriend(); pc.setRemoteDescription(new RTCSessionDescription(offer), function() { }, error);
RTCPeerConnection object.This interface inherits properties from its parent interface, {{domxref("EventTarget")}}.
RTCIceConnectionState that describes the ICE connection state for the connection. When this value changes, a {{event("iceconnectionstatechange")}} event is fired on the object.RTCIceGatheringState that describes the ICE gathering state for the connection.null.RTCIdentityAssertion, that is a couple of a domain name (idp) and a name (name) representing the identity of the remote peer of this connection, once set and verified. If no peer has yet been set and verified, this property will return null. Once set, via the appropriate method, it can't be changed.null.RTCSignalingState that describes the signaling state of the local connection. This state describes the SDP offer, that defines the configuration of the connections like the description of the locally associated objects of type {{domxref("MediaStream")}}, the codec/RTP/RTCP options, the candidates gathered by the ICE Agent. When this value changes, a {{event("signalingstatechange")}} event is fired on the object."closed". It is not expected for the application dealing with the RTCPeerConnection: this is automatically done; an explicit call only allows to anticipate the need.null.new RTCPeerConnection({{domxref("RTCConfiguration")}} configuration, optional {{domxref("MediaConstraints")}} constraints);
Note: While the PeerConnection specification reads like passing an RTCConfiguration object is required, Firefox will supply a default if you don't.
void createOffer({{domxref("RTCSessionDescriptionCallback")}} successCallback, {{domxref("RTCPeerConnectionErrorCallback")}} failureCallback, optional {{domxref("MediaConstraints")}} constraints);
Create offer generates a blob of description data to facilitate a PeerConnection to the local machine. Use this when you've got a remote Peer connection and you want to set up the local one.
var pc = new PeerConnection();
pc.addStream(video);
pc.createOffer(function(desc){
pc.setLocalDescription(desc, function() {
// send the offer to a server that can negotiate with a remote client
});
}
void createAnswer({{domxref("RTCSessionDescriptionCallback")}} successCallback, {{domxref("RTCPeerConnectionErrorCallback")}} failureCallback, optional {{domxref("MediaConstraints")}} constraints)")
Respond to an offer sent from a remote connection.
var pc = new PeerConnection();
pc.setRemoteDescription(new RTCSessionDescription(offer), function() {
pc.createAnswer(function(answer) {
pc.setLocalDescription(answer, function() {
// send the answer to the remote connection
})
})
});
updateIce(optional {{domxref("RTCConfiguration")}} configuration, optional {{domxref("MediaConstraints")}} constraints)
The updateIce method updates the ICE Agent process of gathering local candidates and pinging remote candidates. If there is a mandatory constraint called "IceTransports" it will control how the ICE engine can act. This can be used to limit the use to TURN candidates by a callee to avoid leaking location information prior to the call being accepted. This call may result in a change to the state of the ICE Agent, and may result in a change to media state if it results in connectivity being established.
addIceCandidate ({{domxref("RTCIceCandidate")}} candidate, {{domxref("Function")}} successCallback, {{domxref("RTCPeerConnectionErrorCallback")}} failureCallback);
The addIceCandidate() method provides a remote candidate to the ICE Agent. In addition to being added to the remote description, connectivity checks will be sent to the new candidates as long as the "IceTransports" constraint is not set to "none". This call will result in a change to the connection state of the ICE Agent, and may result in a change to media state if it results in different connectivity being established.
pc.addIceCandidate(new RTCIceCandidate(candidate));
{{domxref("RTCDataChannel")}} createDataChannel ({{domxref("DOMString")}} label, optional {{domxref("RTCDataChannelInit")}} dataChannelDict);
Creates a data channel for sending non video or audio data across the peer connection
var pc = new PeerConnection();
var channel = pc.createDataChannel("Mydata");
channel.onopen = function(event) {
channel.send('sending a message');
}
channel.onmessage = function(event) { console.log(event.data); }
| Specification | Status | Comment |
|---|---|---|
| {{SpecName('WebRTC 1.0')}} | {{Spec2('WebRTC 1.0')}} | Initial definition. |
| Feature | Chrome | Firefox (Gecko) | Internet Explorer | Opera | Safari (WebKit) |
|---|---|---|---|---|---|
| Basic support | {{CompatVersionUnknown}} |
| Feature | Android | Android Webview | Firefox Mobile (Gecko) | Firefox OS | IE Mobile | Opera Mobile | Safari Mobile | Chrome for Android |
|---|---|---|---|---|---|---|---|---|
| Basic support | {{CompatNo}} | {{CompatVersionUnknown}} | {{CompatVersionUnknown}} |