WebRTC ice candidates

Question

I set up RTCPeerConnection but it only works locally (between 2 laptops on my wireless connection). For other connections I see a black stream. I suspect it is due to the ICE candidates not being properly gathered, they only contain local IPs:

RTCIceCandidate {sdpMLineIndex: 0, sdpMid: "", candidate: "a=candidate:2999745851 1 udp 2113937151 192.168.56.1 51411 typ host generation 0
↵"} app.js:14530
RTCIceCandidate {sdpMLineIndex: 0, sdpMid: "", candidate: "a=candidate:3366620645 1 udp 2113937151 192.168.0.17 44628 typ host generation 0
↵"} app.js:14530
RTCIceCandidate {sdpMLineIndex: 1, sdpMid: "", candidate: "a=candidate:2999745851 1 udp 2113937151 192.168.56.1 51411 typ host generation 0
↵"} app.js:14530
RTCIceCandidate {sdpMLineIndex: 1, sdpMid: "", candidate: "a=candidate:3366620645 1 udp 2113937151 192.168.0.17 44628 typ host generation 0
↵"} 
RTCIceCandidate {sdpMLineIndex: 0, sdpMid: "", candidate: "a=candidate:4233069003 1 tcp 1509957375 192.168.56.1 0 typ host generation 0
↵"} app.js:14507
RTCIceCandidate {sdpMLineIndex: 0, sdpMid: "", candidate: "a=candidate:2250862869 1 tcp 1509957375 192.168.0.17 0 typ host generation 0
↵"} app.js:14507
RTCIceCandidate {sdpMLineIndex: 1, sdpMid: "", candidate: "a=candidate:4233069003 1 tcp 1509957375 192.168.56.1 0 typ host generation 0
↵"} app.js:14507
RTCIceCandidate {sdpMLineIndex: 1, sdpMid: "", candidate: "a=candidate:2250862869 1 tcp 1509957375 192.168.0.17 0 typ host generation 0
↵"} 

Here is the iceServers config:

  this.configuration = {
    'iceServers': [
      {
        'url': 'stun:stun.l.google.com:19302'
      }
    ]
  };

However on another deployment machine this configuration actually works for remote peers and I receive candidates with a public IP.

EDIT

Actually running tests with yet another peer outputs the following:

handling offer from radu1 
caching candidate from radu1 (x 15 - saving them locally because the remote description is not received/set yet and it will throw errors like: Illegal string...)
Set remote description from radu1
Object {sdp: "v=0
↵o=- 7594479116751954142 2 IN IP4 127.0.0.1
↵s…06 label:iuzaFLXbo6HCbnWGdobaYN2gSPQmAFKZQaP1v0
↵", type: "offer"}
sdp: "v=0
↵o=- 7594479116751954142 2 IN IP4 127.0.0.1
↵s=-
↵t=0 0
↵a=group:BUNDLE audio video
↵a=msid-semantic: WMS iuzaFLXbo6HCbnWGdobaYN2gSPQmAFKZQaP1
↵m=audio 1 RTP/SAVPF 111 103 104 0 8 106 105 13 126
↵c=IN IP4 0.0.0.0
↵a=rtcp:1 IN IP4 0.0.0.0
↵a=ice-ufrag:nFjsr4JB2b6hTc4K
↵a=ice-pwd:z3BUY0Mlga5JywRNw9lLGqeF
↵a=ice-options:google-ice
↵a=fingerprint:sha-256 64:76:B6:98:ED:FA:6D:D5:E2:40:B6:FE:98:00:29:F7:28:93:C5:6A:CF:2F:59:D2:B7:82:14:BF:38:FD:3B:83
↵a=setup:actpass
↵a=mid:audio
↵a=extmap:1 urn:ietf:params:rtp-hdrext:ssrc-audio-level
↵a=sendrecv
↵a=rtcp-mux
↵a=crypto:1 AES_CM_128_HMAC_SHA1_80 inline:xGSOTjjxbfNVNAxoRxY6UFHTJY86bFnGqK1p23Tm
↵a=rtpmap:111 opus/48000/2
↵a=fmtp:111 minptime=10
↵a=rtpmap:103 ISAC/16000
↵a=rtpmap:104 ISAC/32000
↵a=rtpmap:0 PCMU/8000
↵a=rtpmap:8 PCMA/8000
↵a=rtpmap:106 CN/32000
↵a=rtpmap:105 CN/16000
↵a=rtpmap:13 CN/8000
↵a=rtpmap:126 telephone-event/8000
↵a=maxptime:60
↵a=ssrc:4260698723 cname:8jJISPnQEaP+YvYy
↵a=ssrc:4260698723 msid:iuzaFLXbo6HCbnWGdobaYN2gSPQmAFKZQaP1 iuzaFLXbo6HCbnWGdobaYN2gSPQmAFKZQaP1a0
↵a=ssrc:4260698723 mslabel:iuzaFLXbo6HCbnWGdobaYN2gSPQmAFKZQaP1
↵a=ssrc:4260698723 label:iuzaFLXbo6HCbnWGdobaYN2gSPQmAFKZQaP1a0
↵m=video 1 RTP/SAVPF 100 116 117
↵c=IN IP4 0.0.0.0
↵a=rtcp:1 IN IP4 0.0.0.0
↵a=ice-ufrag:nFjsr4JB2b6hTc4K
↵a=ice-pwd:z3BUY0Mlga5JywRNw9lLGqeF
↵a=ice-options:google-ice
↵a=fingerprint:sha-256 64:76:B6:98:ED:FA:6D:D5:E2:40:B6:FE:98:00:29:F7:28:93:C5:6A:CF:2F:59:D2:B7:82:14:BF:38:FD:3B:83
↵a=setup:actpass
↵a=mid:video
↵a=extmap:2 urn:ietf:params:rtp-hdrext:toffset
↵a=extmap:3 http://www.webrtc.org/experiments/rtp-hdrext/abs-send-time
↵a=sendrecv
↵a=rtcp-mux
↵a=crypto:1 AES_CM_128_HMAC_SHA1_80 inline:xGSOTjjxbfNVNAxoRxY6UFHTJY86bFnGqK1p23Tm
↵a=rtpmap:100 VP8/90000
↵a=rtcp-fb:100 ccm fir
↵a=rtcp-fb:100 nack
↵a=rtcp-fb:100 goog-remb
↵a=rtpmap:116 red/90000
↵a=rtpmap:117 ulpfec/90000
↵a=ssrc:1805691906 cname:8jJISPnQEaP+YvYy
↵a=ssrc:1805691906 msid:iuzaFLXbo6HCbnWGdobaYN2gSPQmAFKZQaP1 iuzaFLXbo6HCbnWGdobaYN2gSPQmAFKZQaP1v0
↵a=ssrc:1805691906 mslabel:iuzaFLXbo6HCbnWGdobaYN2gSPQmAFKZQaP1
↵a=ssrc:1805691906 label:iuzaFLXbo6HCbnWGdobaYN2gSPQmAFKZQaP1v0
↵"
type: "offer"

RTC: adding stream from radu1
Sending answer to radu1
Set candidate from cache for radu1 (x 15)
RTCIceCandidate {sdpMLineIndex: 0, sdpMid: "", candidate: "a=candidate:826241329 1 udp 2113937151 169.254.159.173 52996 typ host generation 0
↵"}
...

The above results in an peerconnection.iceConnectionState = 'checking'. Is the order of events right for a callee?

1. Receive offer
2. Receive ice candidates from another peer but not saving them because setRemoteDescription callback was not fired
3. Remote description successfully set.
4. Remote stream is received
5. Send answer
6. Add cached candidates

Note that this actual setup works between 2 laptops in my LAN. I can view remote streams. It just doesn't work for different networks, black screen and iceConnectionState = 'checking' What does that mean? How can I solve/debug this problem? Do I need to setup any other STUN/TURN servers?

Answer 1

Solved by properly setting up a STUN/TURN server. Seems that some peers need a TURN server to relay traffic because STUN fails.