How to get remote IP in WebRTC / SDP connection?

Question

Assuming there is a WebRTC connection (RTCPeerConnection) between two peers and only one DataChannel, using sdp-transform, I have this code:

const sdp = sdpTransform.parse(this.connection.currentRemoteDescription.sdp);                   
console.log(sdp.media[0].protocol+"://"+sdp.media[0].connection?.ip+":"+sdp.media[0].port);

I expect to get the IP of the peer I am connected to and the port on the remote side. However, instead I get wrong values, for instance I get the TURN server IP and I know for sure the connection is not over the TURN server as I measure the latency over the DataChannel (i.e. connection is direct on same WiFi network). If I disable the TURN server then I get 0.0.0.0 as the remote IP while I expect to get the remote peer's WiFi assigned IP (ex: 192.168.0.53). This is using latest Chrome on two devices.

The only time I get accurate results is if there is no TURN server and the two devices are not connected to the same WiFi, in that case the external IP of the remote peer is reported in sdp.media[0].connection?.ip .

Answer 1

In general, you cannot.

Before establishing the Peer Connection, the two peers exchange ICE candidates that include the addresses at which they wish to be contacted. If the remote peer has only included TURN server's addresses, then the local peer has no information whatsoever about its own addresses.

In most cases, however, the remote peer will also include ICE candidates that contain its own address. You could, in principle, find the addresses of the remote peer by examining the ICE candidates — check the onicecandidate callback.