FTP is normally unencrypted, using separate control and data channels. The standard port is 21, and most modern routers should recognise and appropriately translate FTP commands sent over this port. It may be necessary to forward certain ports when using Passive FTP.
The FTP server can be configured use Explicit FTP to provide encrypted connections AND to only allow Explicit SSL connection - ie normal unencrypted FTP connections will be refused.
Click a Hotspot on the image below for further information.