async function received(event) {
  const msg = JSON.parse(event.data);
  try {
    switch (msg.type) {
      case "offer": {
        await user.setRemoteDescription(new RTCSessionDescription(msg));
        const answer = await user.createAnswer();
        await setdescription(answer);
        break;
      }
      case "answer": {
        await user.setRemoteDescription(new RTCSessionDescription(msg));
        break;
      }
      case "candidate": {
        const candidate = new RTCIceCandidate(msg.candidate);
        await user.addIceCandidate(candidate);
        break;
      }
    }
  } catch (error) {
    showerror(error);
  }
}