What exactly can CoreBluetooth applications do whilst in the background?

Question

The subject says it all, really. Documentation, insofar as it exists at all, suggests that apps written against the CoreBluetooth framework running on iOS devices can add \"

Answer 1

It is also good to note the behavior of backgrounding and CoreBluetooth related to the iBeacons, although Apple likes to think of this as a CoreLocation functionality:

1. When notifications for an iBeacon region are turned on, they will notify the user of region entry or exit. These notifications can be made to depend on whether the display is on or off. These notifications will work even when the app requesting notifications is in the background. (This much is clear in the documentation).

2. Not so obvious: If you use the iBeacon ranging API, then your app has to be in the foreground. It does not explicitly say this in the documentation-- in fact, one can be mislead to think that ranging should work in the background from the documentation. However, an Apple engineer clarifies this in a post buried somewhere in a long thread on the Apple developer forum, and I've seen this fail too. Ranging will work only in the foreground.

3. One can discover other services being advertised by a peripheral advertising iBeacons. But this will work only in the foreground. So if you want the central to be notified of proximity using iBeacons, and then do some other transactions using other BLE-based services, this will work, but only in the foreground. It will not work in the background. For transactions with BLE-based services in the background, the advertisement has to be a regular BLE advertisement, not an iBeacon. You cannot use an iBeacon advertisement to help the discovery process in the background, and then switch to using BLE-services in the background. (I would have very much liked this to work, but no dice).