[salgernon]

Particularly since NSURLConnection is deprecated in the current SDK. NSURLSession has been available since IOS 7.

While NSURLSession does support resumable downloads, it isn't able to resume uploads.

The needNewBodyStream: delegate is the closest thing, and that is called when first uploading from an NSInoutStream or when a transmission error occurs for an idempotent request, or an auth challenge occurs when some of the stream has been sent. (Streams cannot be rewound.)

Background NSURLSessions can take a file reference to upload, and ideally will perform the upload "at a good time", hopefully while charging and connected to a stable network. (But it won't resume an upload, just retry if possible.)

Disclaimer: I'm "involved", but not speaking for any parties involved. Mostly because I don't get invited to those sorts of parties.