Samba is an open source/free software suite that provides seamless file and print services to SMB/CIFS clients. As of 19 August 2008, 3.2.2 is available for download; 3.2 is interesting, among other reasons, because it provides transport-level encryption.
[describe what a SMB and CIFS client is]
This is software that makes use of tcp/ip to allow the host to interact wtih a Windows client or server.
Tcl developers may find that Samba provides them a way to access and process Windows files while still running code on machines running Unix/Linux/Other operating systems.
Back in 1998, phil at seaotter.com mentioned on a Samba mailing list that he had written a tcl extension that allowed tcl script to do NBM lookups and SMB commands. It was a patch to Samba 1.9.18p10. The URL mentioned in the message ( http://zork.net/~phil/projects.html ) is no longer valid ; I don't know whether it is available elsewhere.
Several versions of the page itself are archived here: http://web.archive.org/web/*/http://zork.net/~phil/projects.html