Q: How to change the default port number for FTP Server?

1. Read General Notes
2. Read How to install FTP Server for File Transfer service?

3. e.g. Assumed that new port number is 77

4. sudo cp /etc/proftpd.conf /etc/proftpd.conf_backup
   sudo gedit /etc/proftpd.conf

5. Find this line

   Port                            21

6. Replace with the following line

   Port                            77

7. Save the edited file (sample)

8. sudo /etc/init.d/proftpd restart