I want some information stored in the database server if disconnected the Internet stored database sqlite when Internet connection to send data to the server (even when the app is closed) What is your suggestion for the job
This cannot be done, your application will work for just a short time in background after you terminate the application.
Read more about the Background Execution on Apples Developer site.
iOS app can't run on background. You can handle changes of connection (wifi , 4g, none) when app is on foreground. Or you can add background task which gives you additional time to save data into database etc.
Method is called beginBackgroundTaskWithName:expirationHandler: in applicationDidEnterBackground. More documentations is here Executing Finite-Length Tasks : https://developer.apple.com/library/content/documentation/iPhone/Conceptual/iPhoneOSProgrammingGuide/BackgroundExecution/BackgroundExecution.html
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I am uploading file to server by using multipart form data with NSURLSession. When the application goes in background I want to suspend the request and resume when application comes in foreground again. So I simply do [session suspend] and [session resume]. This is working fine when the app goes in background only. But if the device gets locked, when going back in foreground and try to resume, I get a network connection lost error. I understand that when device is locked, all open sockets are closed and therefore the issue, but is there some way to make this work without the need of starting the upload from beginning?
You should switch your foreground session to a background session before the app goes to background, and then there is no need to suspend it. Your file will be uploaded by OS while in background (eventually).
Unfortunately, according to the documentation, you need to use a file to perform your background upload.
From "Background Transfer Considerations":
Only upload tasks from a file are supported (uploading from data objects or a stream will fail after the program exits).
(In addition to that, there is no guarantee when or why your app will be terminated. Trying to avoid device locking alone won't be sufficient; there are a myriad other ways your app may be terminated.)
App works without internet and I'm storing user data in CSV file using xcode. When internet is available, I want to send this CSV file over the net weather the app is in terminated or suspended state. Is there a way around to bring app in foreground/background state from terminated/suspended state when internet is available?
Yes, but it will be pretty annoying.
Whenever you loose a server connection to an app's instance, schedule a push notification. When that gets handled (e.g. the device is online and receiving the push), you may start a background task that uploads the data.
Besides abusing the push notification service and annoying your users (because of the decreasing battery life from the persistent networking and constant push notifications), you will need a massive back end to hold connections to all active app installations.
So, yes, but please don't.
Edit:
Since the data may only change when the app is 'alive', can't you rely on background fetch and background upload tasks, queueing unsuccessful uploads?
We are building an iOS iPhone app that needs to check-in with a server on a 12 hour basis. This is needed to let the server know that the app is still using it's service on the server. To our understanding this is possible when the app is in background state (not showing on the foreground) via backgound fetch or remote notifications.
But this is not possbile when the app is not running or terminated, when the app is in these states then there is no way to initiate communication with a server. Is this statement corret? Is it possible initiate the communication after a device bootup, is it then possible to send a small keep alive message to te sever?
The background fetch and responding to remote notifcations is not possible in the not running and termenating states(?), so we cannot use these mecahnisms for this purpose. If that is the case are there any other solutions that we can try? Or is it just not possible?
We looked at many sources on the internet but some say that it is possible and others say it is not.
You might want to take a look at the Silent Push Notifications. Here is the thing, if the app is in background mode or suspended state, you will be fine. If the app was killed by the user, you have a problem.
You can always send a silent push notification, and wait for a service call made from the device to your service. If there is a response, it means the app was in background or suspended, and then you can go ahead and do whatever you need to do. If no request is made, it means that app was killed. Then you might want a sent a non silent push letting the user of that device know that he needs to launch the app or something like that. I don't know how you are going to work around it, but that could be a possibility.
I would tell you to take a look at NSURLSession and Background NSURLSessionConfiguration as well, but you will run into the same issue. If the user manually terminates the app, you need to find a work around to set up that connection to the server, and that will imply the user to somehow launch your application.
I am working on Poker app based on server-client based app. When Poker App goes to the background after some time TCP/IP connection lost because app unable to send/recieve any packet to/from the server. Sever ends socket connection. how can i able to establish connection for long time and update my game UI
The topic you asked for, is called "Background Execution".
First:
You can't update the UI while the app enters the background. But you will be able to finish your API-Requests to the server and save the data on phone while using beginBackgroundTaskWithExpirationHandler. You can use this method to write a block which communicates to your server and handles all the data your app will receive. If the App enters the foreground again, you can use this data received in background to update your UI then.
It is important, that those background tasks have to finish in a short time, so it will be not a good idea here to have an infinite loop. Otherwise, iOS will terminate your process. How much time you really get after your app gets backgrounded is determined by iOS.
Second:
If you want to keep tcp/ip-connections always on even if the app remains in the background, Apple provides a very powerful background mode which enables you to run code for any time in the background. It's called VoIP-Services. Unfortunately your app should provide some VoIP-Stuff to not being rejected by Apple. Here is a good article about those services.
After reading the Apple documentation about the background download with the new iOS7 api (NSURLSession), I'm a bit disappointed. I was sure that Apple was managing the pause/resume over the network availability in the background (or provide an option to do so) but no…
So reading the documentation, this is what we've got:
https://developer.apple.com/library/ios/documentation/cocoa/Conceptual/URLLoadingSystem/NSURLSessionConcepts/NSURLSessionConcepts.html
When any task completes, the NSURLSession object calls the
delegate’s URLSession:task:didCompleteWithError: method with either an
error object, or nil if the task completed successfully.
If the task is a resumable download task, the NSError object’s userInfo dictionary
contains a value for the NSURLSessionDownloadTaskResumeData key. Your
app should use reachability APIs to determine when to retry, and
should then call downloadTaskWithResumeData: or
downloadTaskWithResumeData:completionHandler: to create a new download
task to continue that download. Go to step 3 (creating and resuming
task objects).
So far I understand the solution, but my question is: What architecture is the best to handle the loss of the network and resume downloading in the background?
On my side I'm using reachability and each time the network is available, I resume all tasks (referenced over a NSArray when creating), and suspends them when network is lost. This works well in foreground but for the background I need help on the following points:
If my app has no connectivity in foreground, if I go to the background without connectivity all my tasks remains suspended and won't came back if network is available…
Losing network in background, stop all my downloads/tasks.
Scenario:
In foreground, I start downloading my tasks
I go to background and after 10s switch to "aireplan mode"
All my tasks got an error. So in the method URLSession:task:didCompleteWithError: I resume them using
downloadTaskWithResumeData or if I can't (because some have not
enough resume data) I'm creating a new task without resume-ing it (except if network is back at that time).
Then I put the wifi up
As I'm still in background I cannot trigger a "resume" when network is back without launching the application…
How do I address these points? Have I missed something?
As I'm still in background I cannot trigger a "resume" when network is back without launching the application…
you can use "background fetch"，when the app is launched by fetch，then you can check network and resume the download task.
You should create the NSURLSession with background configurations, then your task is sent to a background demon and your app get called when it is completed.
Implementing:
application:handleEventsForBackgroundURLSession:completionHandler:
in the app delegate - without calling the completionHandler - causes the app to hang around in the background after the device loses its connection whilst suspended. That way, the app can still listen to reachability notifications and restart the download when a network connection becomes available once again. However, this is a pretty dodgy approach and may not pass Apple's app store submission guidelines. Additionally, this approach isn't much help when the connection is lost while the app is in the foreground and the connection regained whilst the app is suspended.
In the end I did the following:
Made use of the application:handleEventsForBackgroundURLSession:completionHandler: notification to pause my downloads in the background.
Made use of the intermittent background fetch notification (ie. application:performFetchWithCompletionHandler:completionHandler) to check connection status and restart any paused downloads. (hat-tip #gugupluto)
This still doesn't provide optimal download performance and may lead users to wonder why their "background download" hasn't finished once they reopen the app, but it seems to be the best we can hope for from Apple for now.