The default port for most FTP servers is 21, and that is how most system administrators will leave it. The majority of FTP clients are configured to use it, and some will not even ask you to change it unless you dig through the configuration. There are, however, a few situations where you might want to change the FTP port for your dedicated server or VPS.
If you do not have other users accessing your server and want to add a little security by making your FTP port something no one would guess, you can easily change the port in ProFTPD or Vsftpd.
To change the port in ProFTPD, edit the configuration file, /etc/proftpd.conf and change the following line:
Replace “21” with whatever port number you want.
To change the port in Vsftpd, edit /etc/vsftpd/vsftpd.conf and change the line:
When you are finished, you should restart your FTP server to force the changes to take effect.
There are a few issues you should note. Before changing the port, make sure the port you want to use is available and not used by another service. Also, after you free up port 21, you should close it in your firewall settings and open whatever port you have opened to replace it.