[cups.development] [RFE] STR #1655: Add SNMP page counter and printer status support to socket and lpd backends

[Jerome Alet]

On Thu, May 01, 2008 at 10:24:44AM -0700, Michael R Sweet wrote:
>
> We rely on printers only accepting a connection when they are not
> busy.  For the class of printers that will use SNMP page counters
> (basically all network printers under $20k), this is a safe
> assumption.
> 
> Once we can connect, we query the page counter and then start
> sending the job.  Once we have finished sending the job, we wait
> for the job to finish and then use the last page counter value to
> get the total number of pages printed.  The wait method depends on
> the protocol - for IPP we query the job status, LPD uses the SNMP
> printer state, and socket uses the shutdown/wait-for-close method.
> 
> Printers that do not support the standard protocols will require
> their own driver or port monitor to collect status, supply, and
> page count information.

The problem is with printers that on paper support the protocol,
but in reality don't... The latest problem of this kind I've encountered
is a printer saying it's "idle" while the page counter was still
increasing, and that printer was in fact never seen in the "printing"
state at all. Needless to say, SNMP retrieved page counters were
incorrect... (was an OKI C5400 FYI).

In my experience several printers have this kind of problems. Is it 
because they are misconfigured by default, buggy, or for some other 
reason, I don't know... If you want to be able to trust what the 
printers report in the general case, it's better to double check 
when possible. This sort of checks should be configurable, ideally. 

bye

Jerome Alet