SFTP: Choose SFTP protocol versions
SFTP protocol exists in several versions (from 1 to 6) which differ in functionality. Development of the SFTP protocol has been suspended at version 6 by the voluntary decision of the working group. Most commonly used version today is version 3.
SecureBlackbox supports versions of SFTP from 2 to 6 (versions 1 and 2 are really not used nowadays).
The version to use is negotiated between the client and the server when the connection is established. You specify the versions you want to use via Versions property of the SFTP server or client class. You can specify more than one version (Versions property is a bit flag or set depending on the language) and the parties will negotiate the most recent version they both support.