I would like to know which hosts (on a local network) can communicate with one another.

That is to say: who is the server? who can communicates with him? Is it all the hosts with ports 139 and 445 open which can talk to the server, or are there some SMB sub-networks (defined with membership of a group, for instance) inside the network?


SMB is a client-server setup, whereby the system hosting the share or service is the server, with TCP ports 445 and/or 139 open. The client (e.g. the system mounting a shared folder) connects to the server's open port(s).

Technically speaking you don't need to involve port 139, since that's the older NetBIOS approach, and you can directly do SMB over 445.

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  • Thanks, I was not very clear, I thought there was some kind of "SMB network", but there is no such thing, right ? I guess if there is a SMB server on a network all other Windows computers can potentially communicate with it through SMB ("net" command exists by default on every windows computer I think). My last question: does a XP can communicate with a windows 7 (as they don't have the same SMB version) ? – ahg8tOPk78 Oct 27 '16 at 11:04
  • SMB is just a network protocol; it isn't a network. It operates on top of existing IP and TCP infrastructure. In general, yes, the SMB protocol versions are mostly backward compatible unless particular features are enforced. For example, Windows XP cannot communicate with modern Windows 10 SMB servers when newer security features are enforced by group/local security policy. – Polynomial Oct 27 '16 at 11:08
  • Ok thanks, one last question: what about WORKGROUPs ? I know there are workgroup in netbios, but what about SMB ? It does not exist ? – ahg8tOPk78 Oct 27 '16 at 11:16
  • Workgroups and domains are a separate concept which SMB just happens to tie into due to the authentication and access control models. They are related only by the fact that Windows uses domains and workgroups as identity grouping techniques, and SMB uses those groupings. – Polynomial Oct 27 '16 at 11:22

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