On this same machine as the server is running, I got WIndows file Explorer to see the FTP directory, hitting the WAN address, logging in as the desired user, and listing directories. It works in Active or Passive modes. So far, so good. (The instructions are out of date, BTW. It likes pasv just fine even if view folders is enabled; in fact that’s the default.)
If I check “Require Secure…” (Control only, or both Control and Data), then it won’t work. Cerberus returns an error 521 Not logged in – Secure authentication required, after receiving the USER line.
This is with putting ftps:// in the URL. It puts it back to ftp:// and doesn’t seem to send AUTH before USER, at all.
The point of this is to make this FTP server look/feel to the client just like a “normal” Windows directory share. I have a strange problem with shares not working on my RAID volumes.
This is an old post but I thought I would update it with more information. Windows Explorer and the built-in FTP client in Windows do not allow any type of secure FTP (such as FTPS, FTPES, or SSH SFTP). The built-in Windows tools only allow unencrypted FTP. You will need a dedicated FTP client to connect using FTPS or SSH SFTP.
If you wish to allow unsecured FTP connections, follow the instructions in this FAQ entry:
How can I configure the server to allow unencrypted FTP connections?