After google the question, it makes me confused. Does every app in iOS has the same DeviceToken?
Here is the Apple Document about the issue.
A device token is an opaque NSData instance that contains a unique identifier assigned by Apple to a specific app on a specific device. Only APNs can decode and read the contents of a device token. Each app instance receives its unique device token when it registers with APNs, and must then forward the token to its provider, as described in Configuring Remote Notification Support. The provider must include the device token in each push notification request that targets the associated device; APNs uses the device token to ensure the notification is delivered only to the unique app-device combination for which it is intended.
Each app has different device token.
A device token is an identifier for the Apple Push Notification System for iOS devices. Apple assigns a Device Token on a per-app basis (iOS 7 and later) which is used as a unique identifier for sending push notifications. Each device has two device tokens per app: one for development, and one for production (ad hoc or app store builds). The tokens are 64 hexadecimal characters.