Re: Use network printer from NetBSD

[Johnny Billquist <bqt%update.uu.se@localhost>]

On 2020-06-26 13:23, Rocky Hotas wrote:
> On giu 25 14:18, Greg Troxel wrote:
>
> > The first thing to understand is what format the printer wants.  Back in
> > the old days, printers were postscript, and you basically had to send
> > them postscript.  (Or HP's PCL.)
>
> Yes, of couse, but how?

By reading the documentation.

> > I think 9100 is what HP called "jetdirect".  I somewhat fuzzily think
> > that connecting to that is just like sending bytes over a serial port.
>
> Yes, it is JetDirect, an HP technology, but also adopted by other
> manufacturers.

Well, yes, HP calls it JetDirect. But that is just a fancy name for 
something that is expected to talk directly to the printed without any 
kind of spooling protocol or functionality. Since HPs printers back in 
the day had names like JetPrinter BlahBlah, JetDirect was just the 
"direct" communication with the JetPrinter...

Essentially, the implications are that through port 9100 you just talk 
directly to the printer. But that still leaves figuring out what format 
the printer wants data in... (For HP printers, it was/is easy, it is 
PCL, and sometimes they also understand other things...)

> > That doesn't really surprise me if the printer expects postscript.  You
> > omitted the model from your email.
>
> As in a previous answer to this thread, it is Brother MFC L2750DN.

Looking at the documentation, the following list of printers supports 
PCL6, BR-Script3 and PDF:

DCP-L2550DN/MFC-L2730DW/MFC-L2750DW.

Any other model apparently do not have any kind of printer emulation 
capability. I suspect BR-Script3 is Brothers own print 
handling/layout/formatting/whatever protocol, and that is the only 
protocol supported on other models.

So you need to get the things you want printed formatted using that 
protocol. Postscript is obviously not supported on any of them, and PCL 
and PDF only on some models.

> > 0) read enough docs/etc. to find out what the printer wants
>
>   <https://download.brother.com/welcome/doc100802/cv_mfcl2750dw_uke_oug_a.pdf>
>
> The user manual seems not to mention anything useful about queues of
> accepted input formats.
> How to correctly guess the requirements of a printer?

It do.
Page 615. "Emulation".

> > 1) Try a postscript file.
>
> Done with netcat. You can check out my reply to JingYuan. I also tried
> it directly: `lpr testfile.ps'. The printer display lights up, shows
> `Receiving data', and then nothing happens.

Yes. The printer does not understand Postscript.

> > 2) what you are basically trying to do is have  a printer configured,
> > just like it was attached, except you it isn't physically attached.
>
> Basically yes.
>
> >    - put it on an Ethernet by itself, hooked up to an extra interface on
> >      a computer [...]
> >
> >    - configure a print server that owns the printer [...]
>
> In my case, security is not an issue and I would like not to install
> something extra, even because I could move the NetBSD host to another
> LAN, and I could need to use another printer.
>
> Moreover, the way you suggest, each printer should be related to a
> host with a CUPS server installed and configured. I imagine this is the
> ideal scenario, but I'm afraid it could be too much, in my case.
>
> >    - make all access go through the daemon.  Mutliple users accessing a
> >      network printer at once is a bit of a mess anyway.
>
> This could be another issue, but I am sure that during my tests I was
> the only one to access the printer.
> Thanks for your suggestions,

Your problems are twofold, I'd say. First, trying to use various daemons 
and ports used by these daemons, but without the protocols, is not working.

The closest is when you talk on port 9100. Then you have a clean 
connection to the actual printer without any daemons involved.
But then you hit the problem that the printer expects a format for the 
things to be printed which you are not giving it. So you are feeding it 
things it don't understand. You're lucky you get nothing, You could be 
getting 200 pages of gibberish as well. :-)

  Johnny

--
Johnny Billquist                  || "I'm on a bus
                                  ||  on a psychedelic trip
email: bqt%softjar.se@localhost             ||  Reading murder books
pdp is alive!                     ||  tryin' to stay hip" - B. Idol