icetest.html

<html>
<head>
	<style>
		* {font-size:6vw;}
	</style>
</head>
<body>
<script>
const stunServers = [
  'stun:stun.l.google.com:19302',
  'stun:stun1.l.google.com:19302',
  'stun:stun.cloudflare.com:3478',
];

async function checkConnectionModes() {
  let hostMode = false;
  let srflxMode = false;

  for (const stunServer of stunServers) {
   try {
      const iceConfig = { iceServers: [{ urls: stunServer }] };
      const rtcPeerConnection = new RTCPeerConnection(iceConfig);

      rtcPeerConnection.createDataChannel(''); // Create a dummy data channel
      const offer = await rtcPeerConnection.createOffer();

      rtcPeerConnection.onicecandidate = (event) => {
        if (event.candidate) {
          // Check the ICE candidate type
          if (event.candidate.candidate.includes('srflx')) {
			if (!srflxMode){
				srflxMode= true;
				document.body.innerHTML += ('SRFLX');
				document.body.innerHTML += ('<br />');
			}
          } else if (event.candidate.candidate.includes('host')) {
			if (!hostMode){
				hostMode = true;
				document.body.innerHTML += ('Host');
				document.body.innerHTML += ('<br />');
			}
          }
        } else {
          // All candidates have been gathered
          rtcPeerConnection.onicecandidate = null; // Remove the event handler
        }
      };
      rtcPeerConnection.setLocalDescription(offer);
    } catch (error) {
      srflxMode = true;
    }
  }
}

checkConnectionModes()

</script>
</body>
</html>