Thanks for your input.
This is what I got:
root@backup:~# netstat -tpan | grep :21
tcp 0 0 0.0.0.0:21 0.0.0.0:* LISTEN 648/inetd
I assume that means inetd is in fact listening on port 21.
Also, I know ProFTPD is accepting connections. I tried 'ftp localhost' and was able to login.
Anyone have an idea? :-/