What does the Passive setting in FTP mean

If you are setting up an FTP server, you would have come accross the setting which says "Allow Passive FTP" or "Passive Mode". This short article explains what Passive FTP means.

In the good old days, FTP needed only two seperate connections, one from the client machine and the other from the FTP server. As networks evolved and machines got behind firewalls and started using NAT, the FTP server could not connect back to originating client machine unless it was specified in the NAT table / rules that it was the destination for FTP client.

The Passive setting resolves this issue, it simply tells both the FTP server and the client machine to make all communications go through the port that was opened by the client computer.

Here is another article that

Here is another article that explains this in a little more detail. Hope it helps. http://blog.jscape.com/jscape/2008/05/what-is-the-d-1.html