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Hostname was NOT found in DNS cache
Trying 141.22.30.79 ...
Connected to sftp.informatik.haw-hamburg.de (141.22.30.79) port 22
Failure establishing ssh session
Closing connection

its an education server and i asked the developer, and he told me everything is fine and works. We can't find the fault. For example it's possible to connect with other tools (FileZilla) to the server and it works.