Bug 16849 - http(s) requests do not detect network is down
Summary: http(s) requests do not detect network is down
Status: RESOLVED ANSWERED
Alias: None
Product: Android
Classification: Xamarin
Component: Mono runtime / AOT Compiler (show other bugs)
Version: 4.12.0
Hardware: PC Windows
: Low normal
Target Milestone: ---
Assignee: Jonathan Pryor
URL:
Depends on:
Blocks:
 
Reported: 2013-12-17 11:53 UTC by Gustavo Armenta
Modified: 2017-06-28 18:50 UTC (History)
2 users (show)

See Also:
Tags:
Is this bug a regression?: ---
Last known good build:


Attachments

Description Gustavo Armenta 2013-12-17 11:53:05 UTC
Start a http(s) request on Xamarin Android or iOS and the server side never returns a response. Disconnect network cable, or on a physical device change to Airplane Mode. The standing request does not trigger a disconnection immediatly.

REPRO
Open attached solution
Run sample in an Android API 15 emulator
Let the sample run for 5 minutes, notice http requests are cancelled every 100 seconds
When a request has just started, disconnect network cable, notice the application does not detect the failure, the request is cancelled after 100 seconds.
Comment 1 Jonathan Pryor 2013-12-17 12:22:18 UTC
I'm not entirely sure what could be done to improve this. I see no events on Android to be notified of when the network is disconnected, which means we're left with POSIX socket(2)/connect(2).

POSIX could error out, e.g. write(2) could error with ENETDOWN, but there's not necessarily any timeliness guarantee for when (if ever) write(2) would error out.

Which is a longwinded way of saying that I have no idea how to solve this, and timeouts are likely the sanest solution anyway.
Comment 2 Tom Opgenorth 2017-06-28 18:50:23 UTC
It is possible to monitor the network connection in Android using the ConnectivityManager class (subject to some restrictions). See https://developer.android.com/training/monitoring-device-state/connectivity-monitoring.html.

An Android application may also register a BroadcastReceiver, listening for `android.net.conn.CONNECTIVITY_CHANGE` actions. Note that starting in Android 7.0 this broadcast receiver must be dynamically registered at runtime.

Finally, one could also use the Firebase Job Dispatcher. This library will allow a background job to execute when network changes happen. The job could then take the appropriate action so that the App can handle the disconnected network.

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