Setting up FTPS (SSL - Secure connection)

FTPS (FTP Secure / FTP-SSL) can be used to encrypt the data sent over the FTP protocol, for login information and filedata.

To make this connection, you are required to set your FTP program to use "Explicit SSL" on port 21.
It is also required that you connect with Active Transfer, and that the active transfer is done using the external IP address for your computer. Some FTP programs can handle this automatically, but there are some where you will have to set up your external IP in the options of the program.

Article from category FTP