Internet problem in background while using SDK 35

[furkanKotic]

When using Android SDK 35 in a Flutter project, if there is any internet connection, all connections are cut off as soon as the application is put in the background. It acts as if the device's internet is turned off.
This problem does not occur on devices with SDK 34 and below.

To try it out, you can create a websocket connection and put the application in the background.

Dart version 3.7.0

Logs when put into background

I/flutter ( 3527): Error: ClientException with SocketException: Software caused connection abort (OS Error: Software caused connection abort, errno = 103), address = example.com, port = 41778, uri=https://example.com
I/flutter ( 3527): Error: ClientException with SocketException: Failed host lookup: 'example.com' (OS Error: No address associated with hostname, errno = 7), uri=https://example.com
I/flutter ( 3527): Error: ClientException with SocketException: Failed host lookup: 'example.com' (OS Error: No address associated with hostname, errno = 7), uri=https://example.com

It was said on the Flutter side that it might be related to Dart: flutter/flutter#164368

[mraleph]

Sounds like OS applying restrictions on networking access. There are multiple situations where Android will do that: consider for example data saver and doze / app-standby. I suggest checking ADB logs to see what is going on with the app.

In any case - if OS takes networking connection away, nothing Dart can do about it. So my suggestion is to use adb and figure out what exactly is going on and then read Android documentation about it.

[furkanKotic]

@mraleph
I think it may be an OS restriction if it stays in the background for a certain period of time. However, the entire internet is cut off in just 2 seconds. Moreover, this is a problem that only occurs in Android 15. The restrictions you mentioned above were announced long ago and have existed since 7-8 SDKs ago.

So I checked the Android SDK 35 changelist but I did not see any new restrictions.

You can test it by establishing a websocket connection in a very simple new project. All connections are cut off as soon as it is put in the background.

[mraleph]

You can test it by establishing a websocket connection in a very simple new project. All connections are cut off as soon as it is put in the background.

There is nothing in Dart's networking stack which checks for app background/foreground status - so if connection cuts off it is Android's networking layer cutting it off. Can't really do anything about that. Have you looked at adb logcat? That should reveal what OS does to an app.

Have you tried reproducing with a simple Java app? Does networking there behave differently?

If Java app maintains connectivity but Dart looses - happy to reopen and investigate.