[Samba] Ancient SMB client issues

[Anders Östling]

I have a customer with a couple of industrial robots running Linux 2.6.34 and Samba 3.4.7 (smbclient -V). They are able to connect to SMB shares on Windows servers IF I "allow unsafe connections”, ie lower the SMB minimum level. The servers are on Windows 2019, and this setup has worked for a couple of years now.

I have created a virtual Debian/Samba 4.19 server with the intention of moving over the SMB shares that the robots need to this server. If I connect from Windows 10 clients to the Samba servers shares, no issues. If I try the same from the robot (ancient SMB) then it fails with the rather bleak “protocol negotiation failed: NT_STATUS_INVALID_NETWORK”. I get this error regardless of the min protocol level (NT1 or SMB2) on the server. 

In short, are we doomed to stay with the unsafe Windows share connections, or is there another way to migrate from Windows to Linux? Maybe running an ancient Samba too, but that does not sound too attractive…