[cups.general] RAW queue en 9100 printing

[Dennis Leeuw]

On 02/28/2013 01:50 PM, Helge Blischke wrote:
> Dennis Leeuw wrote:
>
>> On 02/28/2013 12:47 PM, Helge Blischke wrote:
>>> Dennis Leeuw wrote:
>>>
>>>> Hi all,
>>>>
>>>> For all our windows printer queues we used to use IPP to the printer and
>>>> a RAW queue on CUPS and that worked fine, till a couple of weeks ago we
>>>> received a Xerox WC7556 printer. After a lot of tweaking and testing I
>>>> found that the only solution to make it work is to use port 9100 + RAW
>>>> printing.
>>>>
>>>> When we use IPP and RAW and we send a job that has to print 2 copies,
>>>> only one is printed.
>>>> When we use 9100 and RAW then all works fine.
>>>>
>>>> That fact that we found a solution is great, but I also would like to
>>>> know why. Can someone explain to me what the difference is and how this
>>>> works? Or can someone point me to the direction how to find out what
>>>> goes on?
>>>>
>>>> We are using Windows XP, CUPS 1.4.3 on Ubuntu.
>>>>
>>>> Thanks in advance,
>>>>
>>>> Dennis Leeuw
>>> I guess the IPP issue is due to the fact that in this case IPP job
>>> attributes take precedence over the respective settings of the PostScript
>>> job itself (an issue I already detected some time ago when using the java
>>> based IPP implementation in Xerox DocuTech printers).
>>> CUPS inserts a copies value of 1 in the printing IPP requests (as this is
>>> the default) which corresponds to the command line options for the
>>> filters and backends.
>>> I then hacked the IPP backend (starting with 1.3.5) to discard the copies
>>> attribute from the IPP request unless explicitely specified, so that the
>>> copies spec in the PS job got activated again.
>>> If you are interested, I could send you this (brute force) hack which
>>> could easily adapted to the 1.4.3 backend, but you then need to get the
>>> cups 1.4.3 sources, compile from the sources, and replace the original
>>> ipp backen.
>>>
>>> Helge
>>>
>>
>> Thank you for your explantion this sounds exactly like what might be
>> going on. For now the 9100 printing solution is workable.
>>
>> I am going to put wireshark on the wire, to see if I can find the
>> command where it says 1 copy instead of two. Sounds like another mistery
>> solved.
>>
>> Thanks,
>>
>> Dennis
>
> You only need to inspect the /var/spool/cups/cnnnnn files, where nnnnn is
> the respective job ID with leading zeros and look for "copies" and the
> following binary integer value.
> On the other hand, within the PS job, there will be a PostScript statement
> like
> #copies 2 def
> or
> /NumCopies 2 def
> specifying your 2 copies, but CUPS doew not know about that.
>
> Helge

Cool!
I ran the cnnnnn file through hexdump and after "copies" I get:
00 04 00 00 00 02 21 00

The 02 is the amount of copies, and the "prefix" is always 00 04 00 00 
00". Is that always true or is there a deeper meaning?

Thanks for the help. I am learning a lot today.

Greetings,

Dennis