If your app uses a server on the network that’s under your control, you can arrange for the user to be notified when a significant event takes place on the server. This is called a push notification (or remote notification). The user interface for a push notification is the same as for a local notification (Chapter 26): the user is shown an alert in front of whatever is happening at that moment and can use this alert to launch your app.
For example, the TidBITS News app is about news stories on the TidBITS website. The app’s data comes from an RSS feed, which is refreshed on the server side whenever something changes on the site, such as a new news story being posted. It might be appropriate (and cool) if we were to add push notifications to the server code that refreshes the RSS feed, so that users could be alerted to the fact that they might like to launch TidBITS News and read a newly posted story.
Implementing push notifications is not trivial, and requires cooperation across the network between your app and your server, and between your server and Apple’s push notification server. I’ve never actually tried this, so I’m just describing what the architecture is like; for details, read Apple’s Local and Push Notification Programming Guide.
When developing your app, you obtain from the iOS Provisioning Portal (Chapter 9) credentials identifying your app, and allowing communication between your server and Apple’s push notification server, and between Apple’s push ...