Groups > alt.comp.os.windows-10 > #126489
Re: If you print from Windows 10 to your LAN networked printer - have you also printed from Android? How?

From	"JT" <JT@spam-me-not.invalid>
Newsgroups	alt.comp.os.windows-10, alt.comp.microsoft.windows, comp.periphs.printers
Subject	Re: If you print from Windows 10 to your LAN networked printer - have you also printed from Android? How?
Date	2020-11-30 03:14 +0000
Organization	Aioe.org NNTP Server
Message-ID	<rq1o21$7b2$1@gioia.aioe.org> (permalink)
References	(2 earlier) <rposlm$10j$1@news.mixmin.net> <7ii4sftfg5rn4n7go7emtlrj4o54jltmq2@4ax.com> <rpuapm$9iq$1@news.mixmin.net> <5q87sftsq764b7uidqbl533289bld1bog6@4ax.com> <rq18pg$14tc$1@neodome.net>
Cross-posted to 3 groups.
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Arlen Holder wrote:

> On Sun, 29 Nov 2020 14:59:21 +0100, Michael Logies wrote:
> 
> > if your printer is modern, it has a CUPS server included, 
> > the CUPS client ist on Android. 
> 
> Hi Michael Logies,
> 
> Thank you for your purposefully helpful advice on the CUPS process
> o None of us are paid to help each other so I appreciate your help.
> 
> You help out of your heart and that's what is great about Usenet!
> 
> THANK YOU for being the first to explain how the CUPS process works!
> o Almost all debugging requires knowledge of how the system works.
> 
> I had tried CUPS, and failed, but I didn't even know how it worked!
> o Thank you for explaining that process for us all.
> 
> If the CUPS client is on Android, then I already have that installed.
> o <https://i.postimg.cc/PxdDh7Sv/printing03.jpg> 
> 
> In fact, a CUPS client was the second approach I had tried (after Mopria):
> o <https://i.postimg.cc/xdvmwQ3S/printing02.jpg> 
> 
> However, based on my search results, CUPS "seemed" to only reside on Linux
> which is fine except my dual-boot desktops are mostly on Windows, and,
> worse, I tried like hell to find a CUPS port to Windows.
> o I found something for Windows called CUPSS but it seemed a dead end.
> 
> So I failed with CUPS; but if I had a step-by-step tutorial...
> o I might not have failed (likewise if the CUPS setup were more intuitive).
> 
> > The CUPS client always converts to PDF or
> > forwards a PDF to the CUPS server which converts it for the printer
> > (like a driver on Windows) for its printing. 
> 
> Thank you for explaining what the heck CUPS does as I read the Wikipedia
> & still didn't understand in the least how it applied to Android printing.
> 
> Unfortunately, when I tried using CUPS, I could find no Android tutorial:
> o <https://i.postimg.cc/6qRSK6WY/printing11.jpg> 
> 
> So when it got to this stage, I had no server to give the setup form:
> o <https://i.postimg.cc/9fMnMYX4/printing12.jpg>
> 
> It needs a server:port of the format:
> o <http://server.tld:631/printers/Print...
> 
> Certainly I "guessed" and gave it the printer's IP address:
> o http://192.168.0.20:631
> 
> But that failed.
> o And I gave up on CUPS as I didn't have any step-by-step tutorials.
> 
> Nor did I even understand what I was doing.
> o Up until now, printing has "just worked"; and then you learn nothing.
> 
> > If the printer supports printing PDF natively, the CUPS server has 
> > not to convert. I took my wisdom from:
> > https://wiki.ubuntuusers.de/CUPS/ Funktionsweise von CUPS
> 
> My printer is a typical Hewlett Packard LaserJet 2100tn built in 1999:
> o I really do not know what it supports, but I "think" it's only PCL-5.
>   <http://h10032.www1.hp.com/ctg/Manual/bpl13210>
> 
> o I don't see any mention of CUPS or PDF on its official web page:
> o <https://support.hp.com/us-en/product/hp-laserjet-2100-printer-series/25469/model/14918>
> 
> > > I'm very confused why Windows doesn't seem to need a "print server" 
> > > o Yet, Android seems to need a "print server"
> > 
> > The situation on Window is similiar, I think. You have a print job
> > from a client, which has to be converted in a way, the printer
> > understands. This is done by the printing driver for Windows.
> 
> Thank you for explaining how the printing process works on Windows
> o As I never needed to understand it until now (since Windows "just works")
> 
> Is this a correct data flow based on what you are trying to advise me?
> 1. The Windows application (eg MS Word) opens the file in a native format
> 2. Word "File > Print" sends the native format file to the "printer driver"
> 3. The printer driver receives "native format" & outputs "printer format"
>    (which, for my HP LaserJet 2100tn appears to be "PCL-5")
> 4. The printer driver sends that PCL-5 to the printer IP at 192.168.0.20
>    (I have no idea which port as a port scan shows only port 80 open.)
> 5. The printer prints it because the printer accepts PCL-5 format
> 
> Is that the correct data flow in a typical Windows printing situation?
> o If so, that printer driver is doing a lot of work as it needs to know 
>   a zillion native formats (e.g., MS Word, Irfanview image, VIM text, etc.)
> 
> > On CUPS it is more standardized. If a printer understands PDF, 
> > no conversion by a the CUPS server is needed.
> 
> Half of my problem is I don't understand how printing is supposed to work
> o That can be overcome with a step-by-step tutorial - but there are none
> 
> So it behooves me to understand what you're trying to impart to me!]
> 
> Assuming that the printer can "understand" the PDF format... 
> o Is this how an Android print to that printer is "supposed" to work?
> 1. The Android editing app reads the file in a native format (e.g., JPEG)
> 2. The app's "File > Print" sends native format to its "CUPS client"
> 3. The Android CUPS client converts that native (eg JPEG) format to PDF
> 4. That CUPS client forwards that PDF to the printer at 192.168.1.20:????
> 5. The printer prints it because the printer accepts PDF format
> 
> > > I do not profess nor pretend to know how it works; but it works.
> > 
> > PCL-5 is another standard (from HP), like PDF. If Android generates a
> > PCL output, your printer accepts it as a PCL input.
> 
> Given I haven't seen any evidence my HP LJ2100tn supports PDF, I think I
> _must_ get Android to output PCL, which, so far, I have been able to attain
> only with the combination of two companion programs, where I still need to
> _understand_ the data flow as it's not yet working perfectly:
> 
> I "think" this is the data flow, but I'm not at all sure that it is:
> 1. The LetsPrintDroid "print server" reads native format (e.g., PNG)
> 2. That print server converts that native format (eg PNG) to PCL-5 format
> 3. It then sends the resulting PCL-5 to the printer 192.168.0.20:?
> 4. The printer prints it because the printer accepts PCL format
> 
> For PDF files, for whatever reason, we need to add an Android intermediary:
> 1. The LetsPrintDroid "print server" reads native format (e.g., PDF)
> 2. That print server can't convert that native format (eg PDF) to PCL-5
> 3. So it sends the PDF to "LetsPrintPDF" which sends back a "bitmap"
> 4. The LetsPrintDroid print server" converts that bitmap to PCL-5 format
> 5. LetsPrintDroid then sends the PCL-5 to the printer at 192.168.0.20:?
> 6. The printer prints it because the printer accepts PCL format
> 
> Note: Any of that can be wrong; it's what I "think" the data flow is.
> Note: LetsPrintPDF is a PDF viewer (also image viewer) on its own.
> 
> > > What I need help with is understanding why printing from Windows is easy
> > > o And yet, printing from Android to the same printer is not
> > 
> > If your old windows printer does not support PDF or CUPS, it does not
> > work with Linux/Android out of the box. It`s simple.
> 
> As far as I can tell, the HP LJ 2100tn, built in 1999, doesn't support
> either CUPS or PDF; but it does have something called "Jet Direct", which
> seems to accept something called "RAW" but I can't figure out what that is.
> o What is JetDirect <https://en.wikipedia.org/wiki/JetDirect>
> 
> All I can figure out about "JetDirect" is that it's an Ethernet "NIC".
> o It's what allows me to connect the printer to the SOHO router by CAT5.
> 
> On terminology, I see JetDirect somehow related to "print server" based on:
> o HP LaserJet - Printers that can use HP Jetdirect print servers
> <https://support.hp.com/us-en/document/c04763513>
> 
> But I'm not at all sure what a "print server" even is.
> o Nor if my printer having a JetDirect card makes it a "print server".
> 
> What is a print server anyway? <https://en.wikipedia.org/wiki/Print_server>
> o I looked it up and it seems to be unnecessary for a single printer.
> <https://rjyoung.com/blog/managed-it-services/what-you-need-to-know-about-a-print-server-setup/>
> 
> > Years ago hardware for Postscript/PDF-rendering was too expensive to
> > integrate in every printer. So it was done in software on the Windows
> > machine, which converts e. g. PDFs to GDI for the GDI driver of  the
> > printer. Such printers are called "GDI printers":
> > https://en.wikipedia.org/wiki/Graphics_Device_Interface#GDI_printers
> > 
> > The better ones supported at least PCL, too.
> > But today every new printer should support CUPS/PDF.
> 
> What I desire is to know the normal data flow for an Ethernet'd printer.
> o From Windows (since it just works), and, 
> o From Android (since it needs to be debugged).


HP printers use TCP port 9100 by default


JT

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