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 passive FTP, which uses the PASV command. If you disable this, those users will be required to use active FTP, which uses PORT.
Unless you're sure what you're doing, leave allow-pasv set to yes. Otherwise you risk alienating a lot of users who must use PASV to access FTP sites. Users should have the option of using either active or passive FTP, unless your site has some sort of limitation.