Question

Is it possible to have an iPhone app which carries on listening for data on a port when it is sent to background by the user and if any data comes the app can show a local notification and alert the user? I know the multitasking is deliberately limited but wof it allow for that?

Answer 1

It can but with major caveats:

• First, the system will unregister any Bonjour names you might have established.
• Second, if you’re bound to the WWAN, it will go down even with you listening on it (this is true even in the foreground).
• Third, if your app is not doing anything else in the background (i.e., isn’t registered to provide background music, location events or telephony), you must still shutdown within the time limit for background task completion or be terminated.

So, while you could bind and listen on a socket in the background, for almost all practical purposes, it’s not worth doing and you should rethink your design.