NSURLSession Background File Upload using Bound Streams

Question

History:

I am working on a project for which we need to support:

• Background Upload of files using NSURLSession.
• The server expects file to be uploaded using Content-Type: multipart/form-data
• Previously, I was using NSURLConnection with bound pair of Streams as depicted in this Apple Sample.
• Now, I wish to follow similar approach with NSURLSession(Background Session) by using uploadTaskWithStreamedRequest:.
• I have written a small stand-alone iOS Sample + a PHP server to validate my concept.

Problem: Everything works if app stays in foreground, but if during upload I press the home key, the upload fails after some time with error:

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

Also a little before the upload fails the Write/Producer Stream's NSStreamEventEndEncountered is encountered.

Note: I know the work-around where I can write whole HTTP Post body to a temp file and use NSURLSession's file upload API instead. But above is more appropriate if I can make it work.

Question: Can anyone guess what could be possible reason for the upload getting failed?

Sample Code: I have uploaded the iOS Sample Code + PHP Server Code to drop box. Here is the CODE

Thanks!

Answer 1

You can't upload streamed tasks using Background Configuration. I successfully upload data only in two cases:

1. Download task with data stored in request body.
2. Upload task from file. In that case you will not receive response body.