NcFTPd general.cf file configuration
Don't forget to restart NcFTPd after modifying the general.cf file.
This controls whether remote users are allowed to use active FTP, which uses the PORT command. If you disable this, those users will be required to use passive FTP, which uses PASV.
Unless you're sure what you're doing, leave allow-port set to yes. Otherwise you risk alienating a lot of users. Users should have the option of using either active or passive FTP, unless your site has some sort of limitation.