No response from localhost in iOS Background Mode

Question

The application runs on a iOS mobile device (iPhone\iPad) local server on localhost:25989, when go to the browser, we send a few request http://localhost:25989 but server (application) does not send a response until we return to the application.

This situation is shown in the picture down below

Active – My iOS application Foreground (Server)
Background – Send request to my iOS application Background in any browser (Safari, Chrome, etc.)

UPD: Application already configure for work in Background

Question: How to organize the application code for that working in Background Mode the server can return an answer from localhost:25989?

There is no background mode that allows you to continuously run your app in the background. After a short period after backgrounding, your app will be suspended. — Scriptable, Jul 16 '19 at 09:31
This: https://developer.apple.com/documentation/uikit/app_and_environment/preparing_your_ui_to_run_in_the_background/extending_your_app_s_background_execution_time is your best shot. The time is limited though — Kamil.S, Jul 16 '19 at 10:52

Anonimys · Accepted Answer · 2020-05-08T13:31:13.973

NOTE: Code is Broken for iOS 13+, many part now deprecated by Apple. BGTaskSheduler new class replacing UIBackground.

I solved my problem, by use the following code in my AppDelegate.m file to keep the server running in the background:

...
bool *isBackground = NO;

- (void)extendBackgroundRunningTime
{
    if (isBackground != UIBackgroundTaskInvalid)
        return;

    NSLog(@"Attempting to extend background running time");
    __block Boolean self_terminate = NO; //Do not suspend the application in the background

    isBackground = [[UIApplication sharedApplication] 
    beginBackgroundTaskWithName:@"BackgroundTask" expirationHandler:^
    {
        if (self_terminate)
        {
            NSLog(@"Background task expired by iOS");
            [[UIApplication sharedApplication] endBackgroundTask:isBackground];
            isBackground = UIBackgroundTaskInvalid;
        }
    }];

    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0),^    
    {
        NSLog(@"Background task started");
        while (true)
        {
            if(!isBackground)
            {
                [[UIApplication sharedApplication] endBackgroundTask:isBackground];
                isBackground = UIBackgroundTaskInvalid;
                break;
            }
            if(self_terminate)
                NSLog(@"background time remaining: %8.2f", [UIApplication sharedApplication].backgroundTimeRemaining);
            [NSThread sleepForTimeInterval:2];
        }
    });
}

- (void)applicationDidEnterBackground:(UIApplication *)application {   
    NSLog(@"applicationDidEnterBackground");
    [self extendBackgroundRunningTime];  //Call function for upadte time
    NSLog(@"Time Remaining: %f", [[UIApplication sharedApplication] backgroundTimeRemaining]);
}


- (void)applicationWillEnterForeground:(UIApplication *)application {
    isBackground = NO;
    NSLog(@"Enter Foreground");
}

Now application server can send response from Foreground\Background correctly

Result:

No response from localhost in iOS Background Mode

1 Answers1