Unfortunately, this functionality (creating FTP user accounts) is not defined by the FTP protocol or any of its well-known extensions.
- FTP server might offer some custom commands to achieve this (through SITE command, for example), but we are not aware of any FTP server that would actually do this.
- FTP server might offer this functionality through some custom (non-FTP) protocol.
- Some FTP servers might store user account information in the filesystem or in a database and allow a custom application to access this, making it possible to add new users.
- On some FTP servers, creating user accounts programatically might not even be possible.
- Some FTP servers share the user accounts with the OS. Creating an FTP user account is then the same as creating an OS user account.
Please refer to your FTP server's manual for information about the user database or creating FTP accounts. Or just ask the server vendor. Or let us know what FTP server you use - we are quite familiar with some of them.