> From [EMAIL PROTECTED] Fri Feb 22 21:47:46 2002
> To: Patrick Powell <[EMAIL PROTECTED]>
> Subject: Re: LPRng: HP-4100 Pagecount problem. A possible solution. 
> Date: Sat, 23 Feb 2002 16:01:13 +1100
> From: "C. L. McAvaney" <[EMAIL PROTECTED]>
>


> So does that mean that the ECHO doesn't synchronise as it is documented
> that is should do?
>
> Christopher
>             ,,,
>            (. .)
> /-----.oOO--(_)--OOo.-------------------------------------------------\ 
> |  Christopher McAvaney                       [EMAIL PROTECTED]   |
> |  PhD Candidate                                 [EMAIL PROTECTED]   |
> |                                               [EMAIL PROTECTED]   |
> |  phone: +61+3+52272960                    [EMAIL PROTECTED]   |
> |    fax: +61+3+52272028       http://www.cm.deakin.edu.au/~chrismc   |
> \---------------------------------------------------------------------/

>From the PJL Reference:

 Page 7-2
   To clear any possible unread status responses requested by the
   previous application, upon startup, an application should use
   the ECHO command...

 Page 7-14
  ... Since the status messages are buffered in the printer until they
  are received, the current application may receive status messages
  that were requested by a previous applciation. (This happends in
  situations where the application requests information or unsolicited
  status is enabled, and the application closes before receiving the
  status messages).

Basically, what you get with this is a 'marker' in the output
stream.  It does not provide any indication that the previous
job has completed.  In fact,  my observation is that if you:

a)  connect using TCP/IP
b)  send job
c)  disconnect
d)  send new job
    (with echo)

Then:
  a) some printers refuse connection while previous job is in progress
  b) some printers accept new connection,  but will not accept data
     (sigh...) while previous job is in progress
  c) some printers will accept 'no output jobs' and fake their acceptance
  d) some printers will do c), and only when there is a job with output
     will they then block all additional IO until the previous job is
     finished.
  e) some printers will do d),  but also have the interesting behavior
     of reporting errors (out of paper, jam, etc) FOR THE PREVIOUS JOB
     that is in progress.

Printers that do c) and d) are almost impossible to get accurate
page counts from,  as the 'initial' pagecount value is bogus.

Also,  I have seen a,b,c, and d on the same printer... Depending on the
rev level of the network interface code.


Patrick Powell                 Astart Technologies,
[EMAIL PROTECTED]            9475 Chesapeake Drive, Suite D,
Network and System             San Diego, CA 92123
  Consulting                   858-874-6543 FAX 858-279-8424 
LPRng - Print Spooler (http://www.lprng.com)


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