The program can't work for FTP servers. It seems that it can be used only for local folders. In this matter, if you want to synchronize / back up your FTP server, you can use FileZila. This tool is developed to sync / copy data to and from FTP addresses. After you installed it, simply enter your server's address, you username and password, choose a folder from your computer to sync with, and press Connect button. The program will automatically transfer data to / from the two locations.