On Mon, 30 Nov 2020 13:02:50 GMT, AnthonyL wrote:

As mentioned previously try the Android app Port Scan from the Fdroid
repositiory.

Hi AnthonyL,
Thank you for reminding me of that, which, I openly admit, I had forgotten.
o You'd think a Windows port scan would find open ports on a printer

I use AuroraDroid instead of F-Droid (same thing, only with a better GUI,
e.g., it autosaves APKs, just as I use Aurora Store instead of Google Play)
o Port Authority, Port scanner
https://f-droid.org/en/packages/com.aaronjwood.portauthority/

It turns out I already had that F-Droid app in my "Network" folder:
o https://i.postimg.cc/L4YqhR1P/printing16.jpg

Pressing "Discover Hosts", it found the printer easily at:192.168.1.1
o 192.168.0.20 HP-UX E 9000/889

Then I tapped that particular entry & hit "Scan Well-Known Ports"
o Which scanned the first 1024 ports, finding these "Open Ports"
23 - Telnet
80 - World Wide Web HTTP
280 - http-mgmt
515 - spooler
631 - IPP (Internal Printing Protocol)

That was interesting. For example, noting that CUPS is often using port
631, does that mean my printer is already cups server of its own right?

Curious, I hit the button to scan the entire 65K port range, which found:
23 - Telnet
80 - World Wide Web HTTP
280 - http-mgmt
515 - spooler
631 - IPP (Internal Printing Protocol)
9100 - PDL Data Streaming Port

So there it is, in stark black & white.

Not only is the default PCL-5 printer port clearly 9100
o But, apparently, I have "IPP" (is this the same as CUPS?)

Looking it up, it seems IPP is the _only_ protocol CUPS supports natively:
o Cups protocol: What's the difference between RAW/JetDirect, IPP, IPP14, LPD?
https://unix.stackexchange.com/questions/333296/cups-printing-protocols-whats-the-difference-between-raw-jetdirect-ipp-ipp
--
Together we know more than any one of us can possibly know being all alone.