spoolss back connections to client

Tim Potter tpot at samba.org
Tue Jun 11 05:17:01 GMT 2002

On Tue, Jun 11, 2002 at 11:12:08AM +0200, Tom Vandepoel wrote:

> Since we've switched to spoolss printing (samba 2.2.4) it seems that the
> server is always trying to connect to the client. 
> [2002/06/11 10:52:41, 3] lib/util_sock.c:open_socket_out(843)
>   Connecting to at port 445
> [2002/06/11 10:52:41, 2] lib/util_sock.c:open_socket_out(871)
>   error connecting to (Connection refused)
> [2002/06/11 10:52:41, 3] lib/util_sock.c:open_socket_out(843)
>   Connecting to at port 139
> I've traced this back in the source to the "spoolss_connect_to_client"
> call in rpc_server/srv_spoolss_nt.c. It seems this is used to reply back
> to the client with printing info.

It's actually for the printer notifcation stuff.  I.e if you have a port
monitor open on one machine, then print a document from a second machine,
the port monitor will be notified asynchonrously that a new document
has been spooled.  Under Windows 9x/ME this doesn't happen.  The port
monitor must poll every 15 seconds or so to see if new jobs have been

> However, in our environment, such connections typically fail, as we
> disable the "Server" service on NT/W2K clients as much as possible. In
> those cases, printing still works fine, so I'm starting to wonder if
> these back connections are absolutely needed. They are especially
> annoying when the back connection is made to a firewalled client; it
> slows down response of the print server enormously (the server waits
> until the back connection times out).

I've been poking at these last week and I'm pretty sure if there is an
error creating the back channel connection, it just falls back to polling
mode.  Also, with a back channel connection open when you hit 'Apply' on
a printer properties dialog box the hourglass appears until all notification
data has been sent to connected clients which can slow things down.

> So, I was thinking; is there an smb.conf option (or could it be
> implemented) to disable these back connections? What would the impact be
> if I modified the src_spoolss_replyopenprinter() routine to always
> return false? Would that break anything?

Good idea.  It should affect anything.  If you find any problems with
this post them to the list!



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