Redirection

Example: ftp-proxy

Enable in /etc/rc.conf[.local]

ftpproxy_flags=""

/etc/pf.conf

anchor "ftp-proxy/*"
pass in quick proto tcp to port ftp rdr-to 127.0.0.1 port 8021
pass out proto tcp from $proxy to port ftp

Reverse proxy (in front of your own ftp server) also possible