Realization re UDP138 and the Browse Service

Christopher R. Hertel crh at
Wed Apr 2 03:14:22 GMT 2003

Just a note... something I figured out while working on my book.

There was a complaint a while back (a long while, possibly) that the
datagram service--the MSBrowse Protocol in particular--did not respond to
the correct port.  If, for example, a client opens a high-numbered UDP
port to send a GetBackupListRequest the GetBackupListResponse is sent to
port 138, even though that's not the source port of the original Request.

Turns out that this is correct behavior.  Yes, really.

See, the problem is that the mailslot protocol is not a two-way protocol.  
It's all one-way.  There are no "replies" in the traditional sense.  It's
more like stimulus-response.  Mailslot functions generate a mailslot
message... and that's it.  End of story.  The fact that the original
message illicits a reaction from some other node is secondary.  The
response is also a mailslot message, so it gets sent to port 138.

Weird, yes.  Still, that seems to be the way it was designed.

Chris -)-----

Samba Team --     -)-----   Christopher R. Hertel
jCIFS Team --   -)-----   ubiqx development, uninq.
ubiqx Team --     -)-----   crh at
OnLineBook --    -)-----   crh at

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