If you are looking to change the Ftp port on your server from 21 to a non-standard port say 2121, you need tweak the ‘bind’ option in the Ftp configuration file. On a cPanel server with pure-ftp as a Ftp server, you need to edit the pure-ftpd.conf file
# pico /etc/pure-ftpd.conf
Search for the line:
# Bind 127.0.0.1,21
and add the following line below it
Bind *,2121
where, 2121 is the new port you want the Ftp server to listen to.
Save the Ftp configuration and restart the ftp service.
# service pure-ftpd restart
Using the netstat command you can check if the new port is in ‘LISTEN’ state