title: How to use PubNub publish callback to find out which message to re-publish in case of an error
body: <p>The publish callback in PubNub API returns with a message like below -</p>
  
  <pre><code>[1,"Sent","13729639808030640"]
  </code></pre>
  
  <p>But this does not give any indication as to for which message this callback is for. In case of publish error, the first value in the return array will be 0. But how do you find out which message to re-publish?</p>
  
  <p>The publisher can be publishing messages at a high rate and not waiting to receive the callback before publishing another message. So when the callback is invoked the publisher might have already published 10 more messages.</p>