title: Send GCM notification to an offline device
body: <p>If I am sending a notification to a device, and that device is offline I get something like:</p>
  
  <blockquote>
    <p>Error: Unavailable</p>
  </blockquote>
  
  <p>And I have to resend. </p>
  
  <p>My question is:</p>
  
  <p>Will the GCM server keep these notifications in a queue and automatically resend when the device is online? Or it must be completely handled by me.</p>
  
  <p>Because if the GCM server is going to send them automatically(once the device is online), until it actually sends the notifications, my server assumes they are already sent. How to track the time when the notifications are resent successfully?</p>
  
  <p>I might mark on my server side that the notifications are not sent by looking at the <code>Unavailable error message</code> but cannot make out how to mark them as sent once the GCM successfully sends the notifications.</p>
  
  <p>Thank You </p>