iOS应用程序转到后台后套接字连接被杀死 [英] socket connection killed after iOS app goes to background

问题描述

我使用iPhone应用聊天使用套接字连接与服务器通信。当应用程序移动到后台时，我可以看到服务器能够与应用程序通信大约5分钟。但在此之后，套接字连接被破坏。但是一旦移动到后台，应用程序就会停止执行。为什么套接字连接保持5分钟而不是应用程序执行。苹果指定连接将保持的确切时间。

Iam using an iPhone app chat uses socket connection to communicate with the server. When the app is moved to background i can see that the server is able to communicate with the app for about 5 minutes. But after this time, the socket connection is destroyed. But the app stops executing as soon as it moves to background.Why is it that the socket connection is maintained for 5 minutes but not the app execution.Does apple specify the exact time for which the connection would be maintained.

推荐答案

通过在applicationDidEnterBackground中使用以下代码，您可以获得600秒（10分钟）的最长时间：

You can get a max time of 600 sec(10 min) by using making use of following code in applicationDidEnterBackground:

if ([[UIDevice currentDevice] respondsToSelector:@selector(isMultitaskingSupported)]) { //Check if our iOS version supports multitasking I.E iOS 4
if ([[UIDevice currentDevice] isMultitaskingSupported]) { //Check if device supports mulitasking
    UIApplication *application = [UIApplication sharedApplication]; //Get the shared application instance
    __block UIBackgroundTaskIdentifier background_task; //Create a task object
    background_task = [application beginBackgroundTaskWithExpirationHandler: ^ {
        [application endBackgroundTask: background_task]; //Tell the system that we are done with the tasks
        background_task = UIBackgroundTaskInvalid; //Set the task to be invalid
        //System will be shutting down the app at any point in time now
    }];
    //Background tasks require you to use asyncrous tasks
    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
        //Perform your tasks that your application requires
        NSLog(@"\n\nRunning in the background!\n\n");
        [application endBackgroundTask: background_task]; //End the task so the system knows that you are done with what you need to perform
        background_task = UIBackgroundTaskInvalid; //Invalidate the background_task
    });
  }
}

可在此处找到文档 http://disanji.net/iOS_Doc/#documentation/iPhone/Conceptual/iPhoneOSProgrammingGuide/ BackgroundExecution / BackgroundExecution.html

我刚刚实现了backgroundTaskIdentifier对象并使background_task无效以检查时间，应用程序处于活动状态且运行600秒。您甚至可以使用此

I just implemented the backgroundTaskIdentifier object and Invalidate the background_task to check the time, app was alive and was running 600sec. You can even get the remaining time by using this

NSLog(@"Time remaining: %f", application.backgroundTimeRemaining);

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