Why my WebRTC connection doesn't works at some networks?

Question

I've customized Apprtc project (android version). assume we have four internet connection (from different network connections):

NetA -- NetB

NetC -- NetD

I can connect from NetA to NetB, but i can't connect from NetC to NetD!

I have set turn server and stun server but i don't know what is wrong.

--

When connecting from NetA to NetB (success):

Offer SDP:

"v=0\r\no=- 632333030865012591 2 IN IP4 127.0.0.1\r\ns=-\r\nt=0 0\r\na=group:BUNDLE audio video\r\na=msid-semantic: WMS ARDAMS___\r\nm=audio 9 UDP/TLS/RTP/SAVPF 111 103 9 102 0 8 105 13 126\r\nc=IN IP4 0.0.0.0\r\na=rtcp:9 IN IP4 .............."

"candidate:2580031558 1 udp 2122260223 100.95.184.57 37422 typ host generation 0 ufrag NL4P network-id 3 network-cost 900"

"candidate:411053810 1 udp 1686052607 5.116.182.156 1026 typ srflx raddr 100.95.184.57 rport 37422 generation 0 ufrag NL4P network-id 3 network-cost 900"

"candidate:3902036248 1 udp 41885695 34.197.185.148 52061 typ relay raddr 5.116.182.156 rport 1026 generation 0 ufrag NL4P network-id 3 network-cost 900"

"candidate":"candidate:2786567656 1 udp 25108223 34.197.185.148 52062 typ relay raddr 5.116.182.156 rport 1032 generation 0 ufrag NL4P network-id 3 network-cost 900"

Answer SDP:

"v=0\r\no=- 3736097442176838392 2 IN IP4 127.0.0.1\r\ns=-\r\nt=0 0\r\na=group:BUNDLE audio video\r\na=msid-semantic: WMS ARDAMS___\r\nm=audio 9 UDP/TLS/RTP/SAVPF 111 103 9 102 0 8 105 13 126\r\nc=IN IP4 0.0.0.0\r\na=rtcp:9 IN IP4 0.0.0.0\r\na=ice-ufrag:7upj\r\na............"

"candidate:1892013251 1 udp 2122260223 192.168.7.7 37718 typ host generation 0 ufrag 7upj network-id 3 network-cost 10"

"candidate:3650771734 1 udp 1686052607 151.242.87.74 37718 typ srflx raddr 192.168.7.7 rport 37718 generation 0 ufrag 7upj network-id 3 network-cost 10"

"candidate:3902036248 1 udp 41885695 34.197.185.148 52063 typ relay raddr 151.242.87.74 rport 37718 generation 0 ufrag 7upj network-id 3 network-cost 10"

"candidate":"candidate:2786567656 1 udp 25108223 34.197.185.148 52064 typ relay raddr 151.242.87.74 rport 45889 generation 0 ufrag 7upj network-id 3 network-cost 10"

--

When connecting from NetC to NetD (failed):

Offer SDP:

"v=0\r\no=- 280763199112942253 2 IN IP4 127.0.0.1\r\ns=-\r\nt=0 0\r\na=group:BUNDLE audio video\r\na=msid-semantic: WMS ARDAMS___\r\nm=audio 9 UDP/TLS/RTP/SAVPF 111 103 9 102 0 8 105 13 126\r\nc=IN IP4 0.0.0.0\r\na=rtcp:9 IN IP4 0.0.0.0\r\na=ice-ufrag:UPpi\r\na=ice-pwd:Ow2J0AHuS86I0o0yZ5MOv6a/\r\na=ice-options:renomination\r\na=fingerprint:sha-256................."

"candidate":"candidate:2580031558 1 udp 2122260223 100.95.184.57 34267 typ host generation 0 ufrag UPpi network-id 3 network-cost 900"

"candidate":"candidate:411053810 1 udp 1686052607 5.116.182.156 1287 typ srflx raddr 100.95.184.57 rport 34267 generation 0 ufrag UPpi network-id 3 network-cost 900"

"candidate":"candidate:3902036248 1 udp 41885695 34.197.185.148 58779 typ relay raddr 5.116.182.156 rport 1287 generation 0 ufrag UPpi network-id 3 network-cost 900"

"candidate":"candidate:2786567656 1 udp 25108223 34.197.185.148 58780 typ relay raddr 5.116.182.156 rport 1201 generation 0 ufrag UPpi network-id 3 network-cost 900"

Answer SDP:

"v=0\r\no=- 6478139475592243492 2 IN IP4 127.0.0.1\r\ns=-\r\nt=0 0\r\na=group:BUNDLE audio video\r\na=msid-semantic: WMS ARDAMS___\r\nm=audio 9 UDP/TLS/RTP/SAVPF 111 103 9 102 0 8 105 13 126\r\nc=IN IP4 0.0.0.0\r\na=rtcp:9 IN IP4 0.0.0.0\r\na=ice-ufrag:Js6x\r\na=ice-pwd:5tyUT023mAERirumK7aal+9F\r\na=ice-options:renomination\r\na=fingerprint:sha-256 45:97:7F:BC:37:90:4D:B6:35:E5:23:C8:12:09:5A:43:D7:4B:03:EC:A0:7B:70:EB:E4:DB:12:B8:7B:1C:6E:5D\r\na=setup:active.............."

"candidate","label":0,"id":"audio","candidate":"candidate:1106113138 1 udp 2122260223 192.168.1.169 44238 typ host generation 0 ufrag Js6x network-id 3 network-cost 10"

"candidate":"candidate:3232101574 1 udp 1686052607 151.247.139.59 44238 typ srflx raddr 192.168.1.169 rport 44238 generation 0 ufrag Js6x network-id 3 network-cost 10"

"candidate":"candidate:3902036248 1 udp 41885695 34.197.185.148 58781 typ relay raddr 151.247.139.59 rport 44238 generation 0 ufrag Js6x network-id 3 network-cost 10"

"candidate":"candidate:2786567656 1 udp 25108223 34.197.185.148 58782 typ relay raddr 151.247.139.59 rport 36519 generation 0 ufrag Js6x network-id 3 network-cost 10"

"candidate":"candidate:238873586 1 udp 2122194687 100.116.182.76 48966 typ host generation 0 ufrag Js6x network-id 4 network-cost 900"

"candidate":"candidate:3266434145 1 udp 1685987071 91.251.147.158 16369 typ srflx raddr 100.116.182.76 rport 48966 generation 0 ufrag Js6x network-id 4 network-cost 900"

"candidate":"candidate:3902036248 1 udp 41820159 34.197.185.148 58783 typ relay raddr 91.251.147.158 rport 16369 generation 0 ufrag Js6x network-id 4 network-cost 900"

"candidate":"candidate:2786567656 1 udp 25042687 34.197.185.148 58784 typ relay raddr 91.251.147.158 rport 16222 generation 0 ufrag Js6x network-id 4 network-cost 900"

EDIT :

Thanks to all. I found my problem is from my turn server. I can connect in any situation when using appr.tc ice servers (google turn servers). but i can't connect with my turn server. please check question about my turn server at this page :

Why my turn server doesn't work?

Answer 1

Take a look at this article Introduction to WebRTC protocols.

You need to set up STUN and TURN server, to pass the firewall. If peer is behind a firewall or a router, by connecting only to IP address you will hit router not the requested peer device. etc etc.

Answer 2

I would begin to test my TURN server if it is really working. Disable direct links on your firewall (between NetC and NetD or just block the peer IP) to see if it is working via TURN. If not, then fix your TURN server or it's configuration.