Robert E. <robert@re-factory.de> added the comment:

Concerning the plain-text login. I think a FTPS class should default to
encrypted login (you could use the ftp class if you dont want). In no
way should the login credentials be sent unencrypted on default. Using
another parameter might be a soulution to that, though I would prefer
the library to raise an error if establishing an FTPS connection did not
succeed. The main program could then catch it and decide how to proceed
(using plain ftp or aborting according to a given policy).

Sounds reasonable to me.

Note that FTP is an old and somewhat gnarly protocol, and
doesn't work the way more recent application protocols do. The SSL
module is designed for TCP-based single-connection call-response
protocols, more or less. Doing FTPS right might mean we'd have to
extend it.