server config, <VirtualHost>
0.99.0 and later
The Port directive configures the TCP port which proftpd will listen on while running in standalone mode. It has no effect when used upon a server running in inetd mode (see ServerType). The directive can be used in conjunction with <VirtualHost> in order to run a virtual server on the same IP address as the master server, but listening on a different port.
For any server, either <VirtualHost> or server config, setting Port 0 effectively turns off that server.