Can two iPhone aplications communicate with each other?

Is it possible for two iPhone apps to communicate with each other by any means like sending messages etc?

EDIT: Also is there any way a system app can communicate with our app? For example: If I want to pla开发者_JS百科y a sound when I receive a phone call, then is it feasible?

Thanx in advance.

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Do you mean in realtime? On the same device?

Of course there are uncountable ways to do IPC (pasteboard, -[UIApplication openURL:], via a web-service). The best way to send data depends on the actual use case.

For now two apps cannot run at the same time, so realtime communication would not be possible on one device.

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I think that not directly, they're only allowed to access it's own sandbox. You could approach that using Push on both Applications, using an intermediate server to transfer the data between the two apps.

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Direcctly it is not possible at all

With intermediate Server they can.. i.e.

One application sends message to server That server sends same message to Second Application via Push Notification