c1.createDataChannel('datachannel');
  exchangeIceCandidates(pc1, pc2);
  const offer = await pc1.createOffer();
  await pc2.setRemoteDescription(offer);
  await pc1.setLocalDescription(offer);
  const answer = await pc2.createAnswer();
  await pc1.setRemoteDescription(new RTCSessionDescription({
    type: answer.type,
    sdp: answer.sdp.replace(/a=fingerprint:sha-256 .*/g,
      'a=fingerprint:sha-256 00:00:00:00:00:00:00:00:00:00:00:00:00:' +
      '00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:0