iOS - best practice to send incoming call notifications on VoIP app

Question

The first solution I can think of for the incoming call notification is Apple's Push Notification service. However, it is not guaranteed.. there's a relatively high chance it may get lost.. and in a VoIP app, the incoming call notification is so important that I can't afford to miss it too often...

Thus, I followed the tips and enabled the Background Mode to keep the app alive and listening to any incoming call invite. By right, I should just show local notification when the app gets the incoming call invite. This works pretty well when the app is in background/inactive. HOWEVER, when user kills the app manually, no code will get executed, so the app won't get any incoming call invite in such a condition... And because of this particular scenario, I still have to rely on remote push notification.

What I'm trying to achieve is.. waiting for remote notification first, if it arrives, then do not show local notification anymore. If it's lost, then show local notification so that user will always get notified.

The problem is... I have no way to tell if a remote notification has arrived.

I want to know what is the best practice to handle incoming call notifications for a VoIP app?

Answer 1

From appleDoc Apple Developer Docs. (Updated link)

In iOS 8 and later, voice-over-IP (VoIP) apps register for UIRemoteNotificationTypeVoIP push notifications instead of using this method. Using push notifications eliminates the need for a timeout handler to check in with the VoIP service. Instead, when a calls arrives for the user, the VoIP service sends a VoIP push notification to the user’s device. Upon receiving this notification, the device launches or wakes the app as needed so that it can handle the incoming call.