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
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