RTCPeerConnection.canTrickleIceCandidates

The read-only property RTCPeerConnection.canTrickleIceCandidates returns a Boolean which indicates whether or not the remote peer can accept trickled ICE candidates.

ICE trickling is the process of continuing to send candidates after the initial offer or answer has already been sent to the other peer.

This property is only set after having called RTCPeerConnection.setRemoteDescription(). Ideally, your signaling protocol provides a way to detect trickling support, so that you don't need to rely on this property. A WebRTC browser will always support trickle ICE. If trickling isn't supported, or you aren't able to tell, you can check for a falsy value for this property and then wait until the value of iceGatheringState changes to "completed" before creating and sending the initial offer. That way, the offer contains all of the candidates.

Syntax

 var canTrickle = RTCPeerConnection.canTrickleIceCandidates;

Value

A Boolean that is true if the remote peer can accept trickled ICE candidates and false if it cannot. If no remote peer has been established, this value is null.

Example

var pc = new RTCPeerConnection();
// The following code might be used to handle an offer from a peer when
// it isn't known whether it supports trickle ICE.
pc.setRemoteDescription(remoteOffer)
  .then(_ => pc.createAnswer())
  .then(answer => {
    if (pc.canTrickleIceCandidates) {
      return answer;
    }
    return new Promise(r => {
      pc.addEventListener('icegatheringstatechange', e => {
        if (e.target.iceGatheringState === 'complete') {
          r(answer);
        }
      });
    });
  })
  .then(answer => sendAnswerToPeer(answer)) // signaling message
  .catch(e => handleError(e));

pc.addEventListener('icecandidate', e => {
  if (pc.canTrickleIceCandidates) {
    sendCandidateToPeer(e.candidate); // signaling message
  }
});

Specifications

Specification	Status	Comment
WebRTC 1.0: Real-time Communication Between Browser The definition of 'RTCPeerConnection.canTrickleIceCandidates' in that specification.	Working Draft	Initial specification.

Browser compatibility

See also

• WebRTC
• RTCPeerConnection.addIceCandidate()
• Lifetime of a WebRTC session