Apple Push Notification Service

Apple Push Notification service is a robust and highly efficient service for propagating information to devices iOS. Each device establishes an accredited and encrypted IP connection with the service and receives notifications over this persistent connection.

To send notifications, the provider connects to APNS through a permanent and secure connection. When there is new information to be sent, the provider prepares and sends a notification through the APNS channel, which pushes the notification to the target device.

(https://developer.apple.com/library/ios/documentation/NetworkingInternet/Conceptual/RemoteNotificationsPG/Art/remote_notif_simple_2x.png)

A notification is a short message consisting of two main parts of data: the device token and the payload:

  * The device token identifies the device and application on the client side.

  * The payload is a JSON-defined property list that specifies how the user of an application on a device is to be alerted.

Each provider requires a unique provider certificate and private cryptographic key for validation of its connection to the APN. This certificate, provisioned by Apple, must identify the particular topic published by the provider; the topic is the bundle ID of the client application.

For more information: Apple Developers - Apple Push Notification Service