title: Issue while trying to receive message notifications from Slack
body: <p><strong>About</strong></p>
  <p>I am trying to receive message posted on my server as soon as user post message the message in group or channel or direct in slack.</p>
  <p><strong>App Status</strong></p>
  <p><a href="https://i.stack.imgur.com/KwiLM.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/KwiLM.png" alt="enter image description here" /></a></p>
  <p><strong>Code in the verified file where challenge was posted.</strong></p>
  <pre><code>header('Content-type: application/json');
  $myfile = fopen(&quot;test.txt&quot;, &quot;w&quot;) or die(&quot;Unable to open file!&quot;);
  $data = json_decode(file_get_contents('php://input'), true);
  fwrite($myfile, $data[&quot;challenge&quot;]);
  fclose($myfile);
  $json = '{&quot;challenge&quot;:' . $data[&quot;challenge&quot;] . '}';
  echo json_encode([&quot;challenge&quot; =&gt; $json]);
  </code></pre>
  <p><strong>Question</strong></p>
  <p>Now that the above url has been verified successfully, I am still not able to receive the posted messages. I was expecting messages posted at same url which was used to verify challenge parameter. Is that correct?</p>
  <p>Am I missing anything retrieving the messages posted on my server?</p>
  <p><strong>Update - 1</strong></p>
  <p>Due to some reasons I am not even able to verify the url anymore. My server is not receiving any data. I am trying to save whatever is being posted my side but it is always blank everytime,</p>