Cannot pair when phone is on the same LAN as the browser about threema-web

[agross]

@dbrgn Thanks for your quick response! I find it exceptional that you decided to open-source Threema Web and accept support requests like this on GitHub! 👍

[dbrgn]

Could you test whether other WebRTC based projects work with the same two devices connected to the same network, e.g. https://appear.in/?

[agross]

@dbrgn appear.in works: same workstations as with Threema, same phone, same LAN for both devices.

[dbrgn]

Can you look at the debug console of your browser (F12)? Does it contain anything interesting? Maybe share a gist to the relevant looking section?

[lgrahl]

Posting the log of the browser would probably be helpful.

Also, using wireshark on the PC to capture stun packets (can be used as a display filter) would help to see if ICE is working between the devices (turn off other WebRTC applications before though).

[agross]

https://www.dropbox.com/sh/t1sfk9nij7sw1x2/AACUPJABO-3n8HHL7Dt3Hr0za?dl=0

Contains WireShark capture, HAR of web requests and the console log. The capture was created after connecting the phone back to the LAN. So session active -> trying to reconnect -> session ended error message.

[lgrahl]

Have you tried using Firefox?

[dbrgn]

What I see is that the ICE connection between the devices is lost about a minute after the connection buildup succeeded (so the webclient was open and working for a minute, right?). If you switch networks, it's normal that the connection is lost. Otherwise we'd need to keep a permanent websocket signaling connection open. This is something that we wanted to avoid to keep the amount of metadata on the server minimal.

On connection loss the webclient tries to auto-reconnect, which fails. This is a known issue, sometimes reconnecting is a big buggy. This will hopefully be fixed in the next release.

The other thing you mentioned is that connecting never succeeds if both devices are in the same network. @agross, was your phone initially in mobile network when you created that log? If yes, could you send another browser log trace with a failed connecting attempt?

[agross]

@dbrgn The issue is that I cannot pair when both devices are on the same LAN. Pairing only succeeds on mobile data. Once paired, I need to be on mobile data to restore a once-paired session. So yes, in order to create the logs I needed to make the switch from mobile data to wifi.

[agross]

@lgrahl FF shows the same behavior as Chrome.

[dbrgn]

@agross But you can reload the browser, open the debug console (F12), attempt to pair and then copy the debug log after pairing fails.

[agross]

I'm on the run right now. I'll send you a capture of a failed pairing attempt later today. The only visible indication of pairing is currently that the phone shows a spinner. No message in the browser UI.

[lgrahl]

I don't even see an attempt in the Wireshark tracefile for direct device-to-device communication. It's always TURN-relayed.
Can you provide another Wireshark tracefile for FF and a log? Please also mention what kind of action you take at what point in time.

[dbrgn]

The only visible indication of pairing is currently that the phone shows a spinner.

If the browser does not react to the connection attempt, that would indicate that the connection from your phone to the signaling server fails already.

You could enable the debug log in the app (Threema > Settings > Troubleshooting > "Log to File"), try to connect again and then send us the logfile (/sdcard/Threema/message_log.txt, doesn't contain any unencrypted or otherwise readable message contents). If you don't want to post it in public, you can also open a support ticket (https://threema.ch/en/support) and reference this comment.

[Anke]

I cannot pair either in WiFi nor in mobile mode. Firefox stops at 99%.

I have Android 4.3 on Galaxy S3 with Bitdefender Mobile Security on board, and I temporarily deactivated browsing security. PC with Win10Pro, Firefox and Chrome (latest builds) and F-Secure (deactivation didn't change anything.

I'm not such an expert, but I'l attach my Threema and Firefox console log files:

message_log.txt
firefox_threemaweb_log.txt

[dbrgn]

@Anke thanks. Your issue is different than the one by the original poster, it appears that you stumbled upon a bug on the app side. We will look into it.

[agross]

Alright, I think I found the culprit. It was due to broken IPv6 connectivity by my ISP.

Normally, the dual stack configuration works, but today the v6 part got broken. By the time I tried pairing the phone it had an IPv6 address which it used to create outgoing connections (that never reached their destination). With mobile data on the other hand the phone only had IPv4 available, so outgoing connections from the phone worked.

[dbrgn]

@agross good that you could solve it! LANs are the easiest case for WebRTC, therefore I was a bit confused why it wouldn't work :)

[dbrgn]

@Anke please follow #38 regarding the 99% bug.