title: "php_connect_nonb() failed: Operation now in progress (115)" happens intermittently
body: <p>We send some files across to a third party with a PHP cron job via FTP.</p>
  
  <p>However sometimes we get the following error:</p>
  
  <pre><code>ErrorException [ 2 ]: ftp_put(): php_connect_nonb() failed: Operation 
  now in progress (115) ~ MODPATH/fileop/classes/Drivers/Fileop/Ftp.php [ 37 ]
  </code></pre>
  
  <p>When I say "sometimes" I mean exactly that; most times it goes across fine but about 1 in 5 times we get that error. It's not to do with the files themselves, because they will go happily if we try again. </p>
  
  <p>We've found similar issues online - relating to a <a href="http://www.elitehosts.com/blog/php-ftp-passive-ftp-server-behind-nat-nightmare/" rel="noreferrer">bug in PHP</a> with NAT devices or to do with firewall configuration but again the implication is that if this were the case it would <em>never</em> work.</p>
  
  <p>So, why would this work some times and not others?</p>