Strange SSLSocket Errors

I use a SSL socket for FTP secure connections. It works with many severs but there are strange errors for some customer ftp servers.

For ConnectionType=SSLSocket.TLSv12

[quote]Socket: Connected event
<- 220 ProFTPD 1.3.6rc2 Server (ProFTPD) [80.74.155.70]
-> AUTH TLS
<- 234 AUTH TLS successful
Socket: Set Secure=True
Socket: Error 337056010[/quote]

What means error 337056010?! I thought SSLSocket.TLSv12 is backwards compatible to earlier versions, because the documentation says:

If I set ConnectionType=SSLSocket.TLSv11, everything works without error.

[quote]Socket: Connected event
<- 220 ProFTPD 1.3.6rc2 Server (ProFTPD) [80.74.155.70]
-> AUTH TLS
<- 234 AUTH TLS successful
Socket: Set Secure=True
Socket: Connected event
-> USER fishbeam
<- 331 Password required for fishbeam
-> PASS ****
<- 230 User fishbeam logged in
-> PBSZ 0

[/quote]

Is this a Xojo related bug? Because here it seams that SSLSocket.TLSv12 is not backwards compatible to SSLSocket.TLSv11.

Use ConnectionType=SSLSocket.SSLv23 for best protocol negotiation.
The other options only support the single protocol specified

Thank you. ConnectionType=SSLSocket.SSLv23 solved it for me.