* if it's a public server DON'T use ftp... Use sftp instead. It's through SSH so if you got ssh enabled (great chances it is), you can simply use Filezilla (Secure FTP).
But I guess that through drupal, you're going with some automatic feature... Better have a look to upload manually the plugin on your server and install it all by ssh (there should be a way).
If you REALLY want to go through ftp, have a look at /etc/inetd.conf
and have a look at the ftp lines (I used vsftp)...
But nowadays, ftp are only useful for public (anonymous) access, while when you want upload and secure access, those should be done with (again
Sorry for the quick and dirty answer, I don't have much time right now, but I'm sure other people might explain you all in depth.