Kurento returns null value in result

I am running a hello-world client example from localhost.
Kurento media server is installed on Amazon ec2 instance. All TCP and UDP ports are opened. For kurento google STUN server is configured and public IP from Amazon assigned to HttpEndPoint (announced IP) I manage to establish socket connection and exchange iceCandidates.

UPDATE Stun server is configured in WebRtcEnpoint.conf.ini like this: stunServerAddress=stun.1.google.com stunServerPort=19302

At the time of this post this STUN seems to work fine.

The last two frames always return like this:

{"id":26,"jsonrpc":"2.0","result":{"sessionId":"4b9642c4-5d42-41e0-ba61-83698b85552f","value":null}}

{"id":27,"jsonrpc":"2.0","result":{"sessionId":"4b9642c4-5d42-41e0-ba61-83698b85552f","value":null}}

So that the value is always null.

Here is the full list of frames exchanged:

{"id":15,"jsonrpc":"2.0","result":{"sessionId":"4b9642c4-5d42-41e0-ba61-83698b85552f","value":null}}    101 
13:20:50.185
{"id":16,"jsonrpc":"2.0","result":{"sessionId":"4b9642c4-5d42-41e0-ba61-83698b85552f","value":null}}    101 
13:20:50.185
{"id":17,"jsonrpc":"2.0","result":{"sessionId":"4b9642c4-5d42-41e0-ba61-83698b85552f","value":null}}    101 
13:20:50.185
{"id":18,"jsonrpc":"2.0","result":{"sessionId":"4b9642c4-5d42-41e0-ba61-83698b85552f","value":null}}    101 
13:20:50.210
{"id":19,"jsonrpc":"2.0","result":{"sessionId":"4b9642c4-5d42-41e0-ba61-83698b85552f","value":null}}    101 
13:20:50.210
{"id":20,"jsonrpc":"2.0","result":{"sessionId":"4b9642c4-5d42-41e0-ba61-83698b85552f","value":null}}    101 
13:20:50.210
{"id":21,"jsonrpc":"2.0","result":{"sessionId":"4b9642c4-5d42-41e0-ba61-83698b85552f","value":null}}    101 
13:20:50.210
{"id":22,"jsonrpc":"2.0","result":{"sessionId":"4b9642c4-5d42-41e0-ba61-83698b85552f","value":null}}    101 
13:20:50.210
{"id":23,"jsonrpc":"2.0","result":{"sessionId":"4b9642c4-5d42-41e0-ba61-83698b85552f","value":null}}    101 
13:20:50.210
{"id":24,"jsonrpc":"2.0","result":{"sessionId":"4b9642c4-5d42-41e0-ba61-83698b85552f","value":"32d60f30-b7c6-4bba-a626-2af81356641d"}}  135 
13:20:50.211
{"id":25,"jsonrpc":"2.0","result":{"sessionId":"4b9642c4-5d42-41e0-ba61-83698b85552f","value":"v=0\r\no=- 3652338053 3652338053 IN IP4 0.0.0.0\r\ns=Kurento Media Server\r\nc=IN IP4 0.0.0.0\r\nt=0 0\r\na=msid-semantic: WMS GQCQVoS3xcQNmo4JJyGzwHIL1YzJ8QPZiQP3\r\na=group:BUNDLE audio video\r\nm=audio 1 RTP/SAVPF 111 0\r\na=rtcp:9 IN IP4 0.0.0.0\r\na=extmap:3 http://www.webrtc.org/experiments/rtp-hdrext/abs-send-time\r\na=rtpmap:111 opus/48000/2\r\na=rtpmap:0 PCMU/8000\r\na=setup:active\r\na=mid:audio\r\na=sendrecv\r\na=rtcp-mux\r\na=fmtp:111 minptime=10; useinbandfec=1\r\na=maxptime:60\r\na=ssrc:142379529 cname:user3741506464@host-cb3eed9a\r\na=ice-ufrag:Rk14\r\na=ice-pwd:N8cBI2tYxNA96MBRt33lr/\r\na=fingerprint:sha-256 60:F6:3A:EB:47:7E:01:9C:B1:A8:7A:F2:4A:6A:98:A0:E9:1B:04:64:E9:76:04:AF:2F:19:96:FC:27:38:4D:B7\r\nm=video 1 RTP/SAVPF 100\r\nb=AS:500\r\na=rtcp:9 IN IP4 0.0.0.0\r\na=extmap:3 http://www.webrtc.org/experiments/rtp-hdrext/abs-send-time\r\na=rtpmap:100 VP8/90000\r\na=rtcp-fb:100 ccm fir\r\na=rtcp-fb:100 nack\r\na=rtcp-fb:100 nack pli\r\na=rtcp-fb:100 goog-remb\r\na=setup:active\r\na=mid:video\r\na=sendrecv\r\na=rtcp-mux\r\na=ssrc:3535835016 cname:user3741506464@host-cb3eed9a\r\na=ice-ufrag:Rk14\r\na=ice-pwd:N8cBI2tYxNA96MBRt33lr/\r\na=fingerprint:sha-256 60:F6:3A:EB:47:7E:01:9C:B1:A8:7A:F2:4A:6A:98:A0:E9:1B:04:64:E9:76:04:AF:2F:19:96:FC:27:38:4D:B7\r\n"}}    1389    
13:20:50.211
{"jsonrpc":"2.0","method":"onEvent","params":{"value":{"data":{"candidate":{"__module__":"kurento","__type__":"IceCandidate","candidate":"candidate:1 1 UDP 2013266431 10.189.139.160 44044 typ host","sdpMLineIndex":0,"sdpMid":"audio"},"source":"a7d787c2-c252-47e5-b576-8923f69886a0_kurento.MediaPipeline/73f8d561-6349-4d1d-b2e6-9e2743e0c8d2_kurento.WebRtcEndpoint","tags":[],"timestamp":"1443349253","type":"OnIceCandidate"},"object":"a7d787c2-c252-47e5-b576-8923f69886a0_kurento.MediaPipeline/73f8d561-6349-4d1d-b2e6-9e2743e0c8d2_kurento.WebRtcEndpoint","type":"OnIceCandidate"}}}    581 
13:20:50.215
{"jsonrpc":"2.0","method":"onEvent","params":{"value":{"data":{"candidate":{"__module__":"kurento","__type__":"IceCandidate","candidate":"candidate:1 1 UDP 2013266431 10.189.139.160 44044 typ host","sdpMLineIndex":1,"sdpMid":"video"},"source":"a7d787c2-c252-47e5-b576-8923f69886a0_kurento.MediaPipeline/73f8d561-6349-4d1d-b2e6-9e2743e0c8d2_kurento.WebRtcEndpoint","tags":[],"timestamp":"1443349253","type":"OnIceCandidate"},"object":"a7d787c2-c252-47e5-b576-8923f69886a0_kurento.MediaPipeline/73f8d561-6349-4d1d-b2e6-9e2743e0c8d2_kurento.WebRtcEndpoint","type":"OnIceCandidate"}}}    581 
13:20:50.215
{"jsonrpc":"2.0","method":"onEvent","params":{"value":{"data":{"candidate":{"__module__":"kurento","__type__":"IceCandidate","candidate":"candidate:1 2 UDP 2013266430 10.189.139.160 46539 typ host","sdpMLineIndex":0,"sdpMid":"audio"},"source":"a7d787c2-c252-47e5-b576-8923f69886a0_kurento.MediaPipeline/73f8d561-6349-4d1d-b2e6-9e2743e0c8d2_kurento.WebRtcEndpoint","tags":[],"timestamp":"1443349253","type":"OnIceCandidate"},"object":"a7d787c2-c252-47e5-b576-8923f69886a0_kurento.MediaPipeline/73f8d561-6349-4d1d-b2e6-9e2743e0c8d2_kurento.WebRtcEndpoint","type":"OnIceCandidate"}}}    581 
13:20:50.215
{"jsonrpc":"2.0","method":"onEvent","params":{"value":{"data":{"candidate":{"__module__":"kurento","__type__":"IceCandidate","candidate":"candidate:1 2 UDP 2013266430 10.189.139.160 46539 typ host","sdpMLineIndex":1,"sdpMid":"video"},"source":"a7d787c2-c252-47e5-b576-8923f69886a0_kurento.MediaPipeline/73f8d561-6349-4d1d-b2e6-9e2743e0c8d2_kurento.WebRtcEndpoint","tags":[],"timestamp":"1443349253","type":"OnIceCandidate"},"object":"a7d787c2-c252-47e5-b576-8923f69886a0_kurento.MediaPipeline/73f8d561-6349-4d1d-b2e6-9e2743e0c8d2_kurento.WebRtcEndpoint","type":"OnIceCandidate"}}}    581 
13:20:50.535
{"id":26,"jsonrpc":"2.0","result":{"sessionId":"4b9642c4-5d42-41e0-ba61-83698b85552f","value":null}}    101 
13:20:50.535
{"id":27,"jsonrpc":"2.0","result":{"sessionId":"4b9642c4-5d42-41e0-ba61-83698b85552f","value":null}}    101 
13:20:50.53

Solution

Your KMS is not generating STUN candidates, as you can see from this frames

13:20:50.211
{"jsonrpc":"2.0","method":"onEvent","params":{"value":{"data":{"candidate":{"__module__":"kurento","__type__":"IceCandidate","candidate":"candidate:1 1 UDP 2013266431 10.189.139.160 44044 typ host","sdpMLineIndex":0,"sdpMid":"audio"},"source":"a7d787c2-c252-47e5-b576-8923f69886a0_kurento.MediaPipeline/73f8d561-6349-4d1d-b2e6-9e2743e0c8d2_kurento.WebRtcEndpoint","tags":[],"timestamp":"1443349253","type":"OnIceCandidate"},"object":"a7d787c2-c252-47e5-b576-8923f69886a0_kurento.MediaPipeline/73f8d561-6349-4d1d-b2e6-9e2743e0c8d2_kurento.WebRtcEndpoint","type":"OnIceCandidate"}}}    581 
13:20:50.215
{"jsonrpc":"2.0","method":"onEvent","params":{"value":{"data":{"candidate":{"__module__":"kurento","__type__":"IceCandidate","candidate":"candidate:1 1 UDP 2013266431 10.189.139.160 44044 typ host","sdpMLineIndex":1,"sdpMid":"video"},"source":"a7d787c2-c252-47e5-b576-8923f69886a0_kurento.MediaPipeline/73f8d561-6349-4d1d-b2e6-9e2743e0c8d2_kurento.WebRtcEndpoint","tags":[],"timestamp":"1443349253","type":"OnIceCandidate"},"object":"a7d787c2-c252-47e5-b576-8923f69886a0_kurento.MediaPipeline/73f8d561-6349-4d1d-b2e6-9e2743e0c8d2_kurento.WebRtcEndpoint","type":"OnIceCandidate"}}}    581 
13:20:50.215
{"jsonrpc":"2.0","method":"onEvent","params":{"value":{"data":{"candidate":{"__module__":"kurento","__type__":"IceCandidate","candidate":"candidate:1 2 UDP 2013266430 10.189.139.160 46539 typ host","sdpMLineIndex":0,"sdpMid":"audio"},"source":"a7d787c2-c252-47e5-b576-8923f69886a0_kurento.MediaPipeline/73f8d561-6349-4d1d-b2e6-9e2743e0c8d2_kurento.WebRtcEndpoint","tags":[],"timestamp":"1443349253","type":"OnIceCandidate"},"object":"a7d787c2-c252-47e5-b576-8923f69886a0_kurento.MediaPipeline/73f8d561-6349-4d1d-b2e6-9e2743e0c8d2_kurento.WebRtcEndpoint","type":"OnIceCandidate"}}}    581 
13:20:50.215
{"jsonrpc":"2.0","method":"onEvent","params":{"value":{"data":{"candidate":{"__module__":"kurento","__type__":"IceCandidate","candidate":"candidate:1 2 UDP 2013266430 10.189.139.160 46539 typ host","sdpMLineIndex":1,"sdpMid":"video"},"source":"a7d787c2-c252-47e5-b576-8923f69886a0_kurento.MediaPipeline/73f8d561-6349-4d1d-b2e6-9e2743e0c8d2_kurento.WebRtcEndpoint","tags":[],"timestamp":"1443349253","type":"OnIceCandidate"},"object":"a7d787c2-c252-47e5-b576-8923f69886a0_kurento.MediaPipeline/73f8d561-6349-4d1d-b2e6-9e2743e0c8d2_kurento.WebRtcEndpoint","type":"OnIceCandidate"}}}    581

That means that either your STUN configuration is not right, or that the STUN server configured is not working. You can have a look at this list of public STUN servers, and remember that you can only use IPs in your KMS configuration, as libnice does not accept CNAMEs.

Sidenote: HttpEndPoint configuration does not have any influence in WebRTC functionality

EDIT 1

You are using CNAMEs in your STUN configuration, which is not supported. Please read this part of the documentation about how to configure KMS to use STUN/TURN. It should be something like this

stunServerAddress=173.194.66.127
stunServerPort=19302

Make sure that the server you use is working. You might need to check a couple of them.