RTCPeerConnection.onicecandidate

The RTCPeerConnection property onicecandidate property is an EventHandler which specifies a function to be called when the icecandidate event occurs on an RTCPeerConnection instance. This happens whenever the local ICE agent needs to deliver a message to the other peer through the signaling server. This lets the ICE agent perform negotiation with the remote peer without the browser itself needing to know any specifics about the technology being used for signaling; implement this method to use whatever messaging technology you choose to send the ICE candidate to the remote peer.

rtcPeerConnection.onicecandidate = eventHandler;

This should be set to a function which you provide that accepts as input an RTCPeerConnectionIceEvent object representing the icecandidate event. The function should deliver the ICE candidate, whose SDP can be found in the event's candidate property, to the remote peer through the signaling server.

If the event's candidate property is null, ICE gathering has finished. This message should not be sent to the remote peer. When this happens, the connection's iceGatheringState has also changed to complete. You don't need to watch for this explicitly; instead, if you need to sense the end of signaling, you should watch for a icegatheringstatechange event indicating that the ICE negotiation has transitioned to the complete state.

The example below, which is based on the code from the article Signaling and video calling, sets up a handler for icecandidate events to send the candidates to the remote peer.

pc.onicecandidate = function(event) {
  if (event.candidate) {
    // Send the candidate to the remote peer
  } else {
    // All ICE candidates have been sent
  }
}

Notice that the end of negotiation is detected here when the event's candidate property is null.

• The icecandidate event and its type, RTCPeerConnectionIceEvent.