dcclose_bug.html

<html>
<meta charset=utf-8>
<button id="button">Close remote</button>
<div id="div"></div>
<script>
const console = { log: msg => div.innerHTML += msg + "<br>" };

const pc1 = new RTCPeerConnection(), pc2 = new RTCPeerConnection();

const dc1 = pc1.createDataChannel("");
dc1.onopen = () => console.log("open");
dc1.onclose = () => console.log("remote closed");
button.onclick = () => pc2.close();

pc1.onnegotiationneeded = async () => {
  await pc1.setLocalDescription(await pc1.createOffer());
  await pc2.setRemoteDescription(pc1.localDescription);
  await pc2.setLocalDescription(await pc2.createAnswer());
  await pc1.setRemoteDescription(pc2.localDescription);
};
pc1.onicecandidate = e => pc2.addIceCandidate(e.candidate);
pc2.onicecandidate = e => pc1.addIceCandidate(e.candidate);
pc2.oniceconnectionstatechange = () => console.log(pc2.iceConnectionState);

</script>
</html>