title: APNS (Apple Push Notification Service) reliability
body: <p>Our app uses APNS to receive Push Notifications. However, our client claims that some of their devices were not receiving notifications and argues to they 'must' make sure the notifications to be delivered 100%. But I have read <a href="http://www.raywenderlich.com/3443/apple-push-notification-services-tutorial-part-12" rel="noreferrer">somewhere</a> that APNS is not 100% reliable and there should be cases which the notifications are not delivered. </p>
  
  <p>I'm currently panic at how we could make sure APNS to received anytime. I have read that <a href="https://stackoverflow.com/questions/6591550/is-apples-push-notification-service-reliable">a case</a> which may APNS not delivered (device may offline). But our test showing that even the device is online (Wifi or 3G), sometimes APNS were not delivered. </p>
  
  <p>Is there any specific case which may APNS will not delivered? Or is there anything we (developers) can do with codes to make sure to receive all notifications? What I have done in the code is just registering the app to remote notification and write didRegisterForRemoteNotificationsWithDeviceToken, then throw the device token to our server. </p>
  
  <p>Any help would be appreciated, for our client almost kill us if ALL of their devices not receiving APNS!</p>