[solved; non-issue] Problems with wifi without internet connection

Unfortunately, these days my home internet connection is down most of the times. So Android will connect to my home wifi, check internet access (which fails) and mark the wifi as such with an exclamation mark in the status bar.

This means, that Android will notify Syncthing, that it has connected to wifi (probably before checking the internet connectivity), but won’t send any traffic through it. I have set Syncthing Android to run in background and only on wifi. As a result Syncthing will run, even though, the traffic is send over mobile data connection.

Additionally, Syncthing will keep running, even when disconnecting wifi. I left home about 4 hours ago and connected to my office wifi an hour later, but Syncthing is running for over 13 hours and the notification is also dated from yesterday.

Fortunately, Syncthing did not consume any mobile data because the only device it syncs with is not available (as the home internet connection is down) and I disabled mobile data for Syncthing in the Android system settings.

@Nutomic Is there anything the Syncthing Android App can do to verify, that traffic is send through wifi and not mobile data, or that the wifi is reported as “having internet connection”

I’m using the current version on an Moto X Style with Android 6.0.1.

There may be a solution in the Syncthing Android app itself (it’s been some time since I was an Android user so I don’t remember), but I do know that you can disable the checking of internet connectivity as described here:

That will get rid of the exclamation point indicator and should eliminate the interference of your LAN traffic by Android. I am not sure / don’t remember what effect this will have on your traffic to the internet when your home connection is down (presumably you want to use mobile data for non-LAN traffic in this case). But this setting is sufficiently easy to change and change back that it’s worth a try.

See #540.

Also, if there’s no internet on a wifi connection, Android will continue to use mobile data, so fixing that problem might not help you.

If those times you have are from the Android settings, that’s expected. The app will always run, even when Syncthing is disabled.

My problem was the other way aroung (was running (and didn’t complain on start) when it shouldn’t).

But it turns out, even with “pros”, sometime the problem is in front of the screen ;). After I noticed a while back, that Syncthing used ~40MB mobile data for no reason, I disabled mobile background data for Syncthing in the Android settings and disabled “only on Wifi” in the App to test it. After that I didn’t enable “only on Wifi” again, as it cannot connect through mobile anymore, and forgot about it :).

If you are rooted, install Afwall and disable data connection for Syncthing (have only wifi/lan enabled). That should stop st to access mobie data.