If you want to change the port that is used to connect to the FTP server, you will need to modify the configuration file then restart the service.
1. Using your preferred text editor such as vi or nano, locate the following lines in the configuration file:
# cat -n /etc/pure-ftpd.conf |sed -n 210,214p
211 # IP address/port to listen to (default=all IP addresses, port 21).
213 Bind 21
2. Change the port number on the "Bind 21" line to the port of your choosing. Make sure that you select a port that is not already in use by another service, and ensure that the port is not blocked by your firewall software or otherwise inaccessible.
3. Restart the FTP service. You can do this via the Home >> Restart Services page in WHM, or via the command line:
4. Confirm the FTP service is now listening on the new port number. For example, I used port 6021:
[root@samtest ~]# lsof -i -nnP |grep :6021
pure-ftpd 12367 root 4u IPv4 4920402 0t0 TCP *:6021 (LISTEN)
pure-ftpd 12367 root 5u IPv6 4920403 0t0 TCP *:6021 (LISTEN)