I'm getting the same thing with the Filezilla server. I'm using the ftps client to make sure the library will do what I need before I start coding -
ftps -h localhost -U xxxx-P yyyy -l . -port 990 -ssl Implicit
Accept invalid server certificate? (Y/N) Y
Remote directory: .
ERROR: The handshake failed due to an unexpected packet format.
I have Filezilla set-up in a very standard basic way and the Filezilla client connects OK on port 990.
ftps connects fine using no ssl or using explicit ssl.
Not too much of an issue as ftps connects the real world ftp server. I've no idea how that one is configured though I see from the welcome message that it's the same version of the Filezilla server that I'm using locally. (0.9.39 beta)
So I presume there's a setting somewhere in the Filezilla server that will resolve the issue - no idea where!