If you want to change your FTP port then follow the steps :
Pure-FTP1) Edit /etc/pure-ftpd.conf and look for the following line:
Before :
QuoteBind 21
After :
QuoteBind 20
Note : 20 is the new port we used put the service on.
2) If necessary, add the new FTP port to your server's firewall.
3) Edit /etc/chkserv.d/ftpd and change the port, which is the first comma-separated entry to the right of '=' on the line in the file, to match the port you put the service on.
ProFTP1) Edit /etc/proftpd.conf and change:
QuotePort 21
2) Then make sure to test to make sure FTP is working before notifying your users !