How can I redirect service requests from one machine to another?
You can redirect FTP (and other service) request with the socket package, available in the ports tree in category ``sysutils''. Simply replace the service's command line to call socket instead, like so:
ftp stream tcp nowait nobody /usr/local/bin/socket socket ftp.example.com ftp
where ftp.example.com and ftp are the host and port to redirect to, respectively.