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What ports need to be redirected to share Microsoft files?

 
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Joined: 09 Oct 2002
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Location: Lausanne, Switzerland

PostPosted: Fri Jun 13, 03 15:34    Post subject: What ports need to be redirected to share Microsoft files? Reply with quote

Microsoft has two ways of sharing files over a network. File sharing is done using Microsoft's SMB (Server Message Block) protocol over the ports below.

All Microsoft OS support
  • TCP port 139
  • UDP ports 137 and 138

Only Windows 2000 and XP support
  • TCP port 445

Windows 2000 will try both methods (if NetBT is enabled) and the one that is responded to first will be chosen. The process of identification used by Windows 2000 is as follows: The Win2K computer sends out a TCP SYNC packet to both port 445 and 139 and whichever responds first with anything other than a TCP RST is selected. If there is no response from either of the ports, the connection will fail.

The old method called NetBT (NetBIOS over TCP/IP), uses UDP ports 137, 138 and TCP 139.

To verify if the remote Windows computer is ready to receive this traffic, open a console connection (DOS Prompt) and enter "netstat -an" and search for the above numbers.

CAUTION: it is not recommended to open these ports to general Internet access. It is best to use these only on a secured connection such as with IPSec or SSH Port Forwarding.
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