WebRTC: Meaning of "initiator ICE candidate error"

[2color]

In the universal-connectivity, we initialise the webrtc transport in js-libp2p as follows:

      webRTC({
        rtcConfiguration: {
          iceServers: [
            {
              // STUN servers help the browser discover its own public IPs
              urls: ['stun:stun.l.google.com:19302', 'stun:global.stun.twilio.com:3478'],
            },
          ],
        },
      }),

When I initiate a WebRTC connection from the browser to another browser peer with the following multiaddr: /ip4/147.28.186.157/udp/9090/webrtc-direct/certhash/uEiBbC9bbdvraVWDvcvCEdJAWDymmUqiJQ964FuyEq0hELw/p2p/12D3KooWGahRw3ZnM4gAyd9FK75v4Bp5keFYTvkcAwhpEm28wbV3/p2p-circuit/webrtc/p2p/12D3KooWNuYo4UdN3eomAngE4DPRwVz5qXxLQsa6njw1TjFJZsNb, I noticed that I get the following error:

What's the exact meaning of this error?

What are some good ways to get a better understanding and debug the state of a webrtc connection?

I should note that this is a connection between two browsers on the same machine and the connection is upgraded successfully to a direct connection.

[achingbrain]

I think it means your browser is failing to resolve the domain name of the configured servers. There's an errorText field in there:

STUN host lookup received error

I don't know if including the stun: protocol at the start of the url string might be tripping it up? Just a guess.

• https://developer.mozilla.org/en-US/docs/Web/API/RTCPeerConnection/icecandidateerror_event

[2color]

I think including stun: is correct based on other examples I've seen in the wild. But since it failed with both STUN servers, I think this may have been related to the network I tried this on.

My hunch is that it's related to IPv6 (see addresses). I'll try it again on a network with IPv6 enabled. But from what I know, IPv6 reliability depends to a large degree on the ISPs ability to route packets, which apparently not all ISPs do well.