title: How to add "DTLS fingerprint" to the offer from android app in WebRtc
body: <p>We are implementing a peer-to-peer audio and video calling app. Though, the android-to-android and web-to-web calls work properly, an exception occurs on the web-app while we try to call from the <strong>android</strong> app to <strong>web</strong>. This exception occurs while setting the remote description on the webapp.</p>
  <p>Exception
  <strong>Uncaught (in promise) DOMException: Failed to execute 'setRemoteDescription' on 'RTCPeerConnection': Failed to set remote offer sdp: Called with SDP without DTLS fingerprint.</strong></p>
  <p>The offer</p>
  <pre><code>{
     &quot;type&quot;:&quot;offer&quot;,
     &quot;sdp&quot;:&quot;v=0\r\no=- 5083258713308557877 2 IN IP4 127.0.0.1\r\ns=-\r\nt=0 0\r\na=group:BUNDLE 0\r\na=msid-semantic: WMS ARDAMS\r\nm=audio 9 RTP\/AVPF 111 103 104 9 102 0 8 106 105 13 110 112 113 126\r\nc=IN IP4 0.0.0.0\r\na=rtcp:9 IN IP4 0.0.0.0\r\na=ice-ufrag:3U6L\r\na=ice-pwd:W8QhzJWp0tU4D1Y3BF08Fq10\r\na=ice-options:trickle renomination\r\na=mid:0\r\na=extmap:1 urn:ietf:params:rtp-hdrext:ssrc-audio-level\r\na=extmap:2 http:\/\/www.webrtc.org\/experiments\/rtp-hdrext\/abs-send-time\r\na=extmap:3 http:\/\/www.ietf.org\/id\/draft-holmer-rmcat-transport-wide-cc-extensions-01\r\na=extmap:4 urn:ietf:params:rtp-hdrext:sdes:mid\r\na=extmap:5 urn:ietf:params:rtp-hdrext:sdes:rtp-stream-id\r\na=extmap:6 urn:ietf:params:rtp-hdrext:sdes:repaired-rtp-stream-id\r\na=sendrecv\r\na=msid:ARDAMS LOCAL_AUDIO_TRACK\r\na=rtcp-mux\r\na=rtpmap:111 opus\/48000\/2\r\na=rtcp-fb:111 transport-cc\r\na=fmtp:111 minptime=10;useinbandfec=1\r\na=rtpmap:103 ISAC\/16000\r\na=rtpmap:104 ISAC\/32000\r\na=rtpmap:9 G722\/8000\r\na=rtpmap:102 ILBC\/8000\r\na=rtpmap:0 PCMU\/8000\r\na=rtpmap:8 PCMA\/8000\r\na=rtpmap:106 CN\/32000\r\na=rtpmap:105 CN\/16000\r\na=rtpmap:13 CN\/8000\r\na=rtpmap:110 telephone-event\/48000\r\na=rtpmap:112 telephone-event\/32000\r\na=rtpmap:113 telephone-event\/16000\r\na=rtpmap:126 telephone-event\/8000\r\na=ssrc:467782680 cname:fnX+hE2E9Qyam6vl\r\na=ssrc:467782680 msid:ARDAMS LOCAL_AUDIO_TRACK\r\na=ssrc:467782680 mslabel:ARDAMS\r\na=ssrc:467782680 label:LOCAL_AUDIO_TRACK\r\n&quot;,
     &quot;call_id&quot;:&quot;cbc7855a-f670-41e6-9b6b-7783a2972707&quot;,
     &quot;caller&quot;:&quot;Test2&quot;,
     &quot;ice_configs&quot;:[
        &quot;&lt;some ice configs&gt;&quot;
     ]
  }
  </code></pre>
  <p>Therefore, I would be appreciate it if someone could let us know what are the possible causes of this exception and how we could fix it.</p>