7 Replies
      Latest reply on Jul 5, 2019 11:38 AM by hubauer
      fdsafasdfdas Level 1 Level 1 (0 points)

        I'm getting a

        Error Domain=NSURLErrorDomain Code=-997 "Lost connection to background transfer service"

        when I lock my screen after starting a background download process. I'm using Alamofire but I assume this would happen on a regular URLSession as well (because internally Alamofire is using URLSession). The downloads continue to work if I soft close the app but as soon as I lock my device, it start throwing this error.

         

        The URLSession is created this way:

         

          let config = URLSessionConfiguration.background(withIdentifier: "MySession")
          config.isDiscretionary = true
          config.sessionSendsLaunchEvents = true
          config.shouldUseExtendedBackgroundIdleMode = true

         

        I looked at the Console to see if any daemon crashed but couldn't find any. I see three errors right after locking the screen:

         

        BKLogEvent: couldn't find CombinedSequence properties
        Task <>.<48> finished with error - code: -999
        Task <>.<48> load failed with error Error Domain=NSURLErrorDomain Code=-997 "Lost connection to background transfer service" UserInfo={NSErrorFailingURLStringKey=, NSErrorFailingURLKey=, _NSURLErrorRelatedURLSessionTaskErrorKey=, _NSURLErrorFailingURLSessionTaskErrorKey=, NSLocalizedDescription=Lost connection to background transfer service} [-997]
        

         

        The error._userInfo is:

        ▿ Optional<AnyObject>
          ▿ some : 5 elements
          ▿ 0 : 2 elements
          - key : NSErrorFailingURLStringKey
          - value : https://www.myweb.com/api
          ▿ 1 : 2 elements
          - key : NSErrorFailingURLKey
          - value : https://www.myweb.com/api
          ▿ 2 : 2 elements
          - key : _NSURLErrorRelatedURLSessionTaskErrorKey
          ▿ value : 2 elements
          - 0 : BackgroundDataTask <C39E-2FC73>.<27>
          - 1 : LocalDataTask <C39E-2FC73>.<27>
          ▿ 3 : 2 elements
          - key : _NSURLErrorFailingURLSessionTaskErrorKey
          - value : BackgroundDataTask <C39E-2FC73>.<27>
          ▿ 4 : 2 elements
          - key : NSLocalizedDescription
          - value : Lost connection to background transfer service

         

         

        I've about 300 of these background tasks. They will continue to work as long as I don't lock my device but as soon as I lock the device it starts throwing this error. My initial thought was that it was some sort of File protection errors but the userInfo from error doesn't point that way.