[cups.general] DNS-SD-(Zeroconf)-based CUPS backend to discover network printers

[Till Kamppeter]

I have met Mike Sweet on the Printing Summit in Montreal this week and 
he suggests letting the dnssd backend display the CUPS (IPP) queues of 
Mac OS X workstations but not of other workstations. And I think even 
better could be listing the queues of remote CUPS servers if they do not 
broadcast their queues via CUPS' native IPP method.

Now I have two questions:

1. How can on determine the operating system which a remote machine is 
running, preferably by means of simple command line tools?

2. How can one easily determine whether a remote CUPS server is 
broadcasting its queues, without waiting up to 30 sec for the next 
broadcast?

    Till

Till Kamppeter wrote:
> Hi,
> 
> I have written a small Perl program around the command line 
> "avahi-browse -k -t -v -r -a" to be run as a CUPS backend to discover 
> network printers. It is used the same way as the "snmp" backend. You put 
> it into /usr/lib/cups/backend/ and make it executable. The whenever a 
> printer setup tool asks CUPS to look for available printers (or if you 
> call "lpinfo -v") the program gets called and CUPS will list the 
> discovered printers.
> 
> As it does fairly the same as "snmp" but only based on another method 
> you can deactivate "snmp" via
> 
> chmod -x /usr/lib/cups/backend/snmp
> 
> and avoid duplicate results. You can also have both running to get a 
> more reliable scan including old printers not supporting DNS-SD and 
> newer cheap printers (like the HP LaserJet 2600n) not supporting SNMP.
> 
> The backend also reports make/model info so that printer setup tools can 
> auto-select PPDs/drivers. In addition, it even discovers the PDLs of the 
> printers, this way printer setup tools can react muchg more 
> intelligently on unknown printer models, assigning PPDs like "Generic 
> PCL-6/XL printer", and so the unknown printer "just works", too.
> 
> If a printer has more that one access protocol, the highest priority is 
> on socket, after that LPD, and IPP at last. To avoid discovering the 
> print queues of CUPS 1.3.x servers as IPP printers every result on IPs 
> which also appear as a computer are discarded.
> 
> If a printer has more than one port for TCP/Socket or more than one 
> internal queue for LPD or IPP, all ports/queues get listed.
> 
> In my small network (2 comnputers, 3 network printers) there are no 
> visible speed differences. Please report your experience in big networks.
> 
> Here is the tool (License: GPL) for download:
> 
> http://www.openprinting.org/download/printing/dnssd
> 
> Needs Perl and Avahi.
> 
> I want to ask all of you to test this tool and compare it with the SNMP 
> backend, especially in big networks and with non-HP printers.
> 
> - Is it faster?
> - Is it more reliable (same results on repeated calls)?
> - Does it discover more printers?
> - Does it hang on certain printer models?
> 
> Thank you in advance for every test report.
> 
>    Till
>