[avahi] "Unable to locate printer" -- Printer name confusion (bug?)

[Tom Pusateri]

You can troubleshoot this by separating mDNS resolution from service discovery.

If you can ping either name with .local appended, mDNS resolution is working.

You should have the nss_mdns pkg installed and your /etc/nsswitch.conf should have a hosts line something like:

hosts: files mdns dns

Then ping bromance.local or BRN001BA9A2273F.local and see which one responds.

Then you can search for the printer service once you can ping.

From FreeBSD:
avahi-browse _printer._tcp
or
avahi-browse _ipp._tcp

depending on the printer you have.

From a macOS machine:
dns-sd -B _printer._tcp local
or
dns-sd -B _ipp._tcp local

If you get a response here, you’re all set. If not, describe what works and what doesn’t.

Tom


> On Jun 7, 2019, at 10:29 PM, Ronald F. Guilmette <rfg at tristatelogic.com> wrote:
> 
> 
> I've been trying, of late, to set up a fresh new FreeBSD system, and to
> enable printing therefrom, and so far I've made just about every mistake
> that it is possible to make.  (The old saying is that software cannot
> be made foolproof because they keep on inventing bigger fools.  In this
> case, that would be me.)
> 
> Anyway, after much struggle I've managed to get CUPS and the cupsd daemon
> up and running, and I've managed to add my specific local networked printer
> (Brother MFC-7860DW) to CUPS so that it (CUPS) now knows that it exists as
> a printer.  I've also enabled both dbus and the avahi daemon to correctly
> start up at boot time.
> 
> Now I can print, e.g. from applications like firefox, HOWEVER, those print
> jobs are consistantly failing to actually be sent to the printer, and CUPS
> is consistantly showing me the following error when I go to look at these
> (failed) print jobs via CPUS' in-built web interfacce (http://localhost:631):
> 
> 	Unable to locate printer "bromance"
> 
> I think that I may possibly have figured out the cause of the problem here,
> or maybe not.  I'm hoping that you folks will tell me if I have or not.
> 
> Quite simply, several days ago, as I was starting this grand adventure, I saw
> again something I had seen many times before which was that my networked
> printer had an ugly and not very memorable sort of name name which was
> showing up in the clients listing on my ASUS router.  The name being shown
> was always "BR" followed by some long string of numbers... not very memorable.
> 
> So I took it upon myself to change the printer name, via the printer control
> panel, to "bromance".  This I apparently did successfully.  Note in particular
> the next-to-last line of this output from the bundled "snmp" program that
> comes packaged with the CUPS 2.x.x package:
> 
>    https://pastebin.com/raw/1zp7GBui
> 
> So anyway, bottom line, I do believe that CUPS knows my printer by the name
> "bromance" and that it puts things/jobs into its spool along with instructions
> that they should ultimately be sent to "bromance".
> 
> While trying to debug my printing problem, I stumbled upon this helpful page
> which gave me a hint as to how I could find the name that avahi is associating
> with my printer's static IP address (192.168.1.57):
> 
>    https://bbs.archlinux.org/viewtopic.php?id=92011
> 
> I took the hint from that page and ran the following command, which produced
> the output shown:
> 
>    % avahi-resolve-host-name -a 192.168.1.57
>    192.168.1.57    BRN001BA9A2273F.local
> 
> From this I infer that avahi is... for reasons I am none too clear on...
> still of the opinion that the correct and proper name for my local networked
> printer is actually still "BRN001BA9A2273F".
> 
> This, it seems to me, might possibly explain why CUPS is ready, willing, and
> able to believe that my local priter is named "bromance" but when it (CUPS)
> actually goes to try to actually send a job to that printer, it somehow
> loses its mind and can no longer even find the bleepin' thing.
> 
> What say you avahi folks?  Is this a plausible explanation for my ongoing
> inability to print?
> 
> And why is avahi-daemon picking up the (old/original) name for this printer,
> even after I have used the printer's control panel to change its name?  And
> where is it even getting this old name (BRN001BA9A2273F) from anyway??  That
> name  doesn't seem to be being provided as part of any SNMP data, so I am
> totally in the dark about where and how avahi is even finding or obtaining
> it.
> 
> This is all most perplexing.
> 
> I guess that I'll probably try and see if I can use the printer's control
> panel to switch its name back to BRN001BA9A2273F, and then reboot everything
> and try printing again, but if that doesn't work them I'm entirely screwed,
> because I don't know what else to even try, and I don't have the first clue
> of how to debug any of this any further.
> 
> Any and all help will be appreciated.
> 
> 
> Reards,
> rfg
> 
> 
> P.S. I have looked at my /usr/local/ect/avahi/hosts file and there is nothing
> in there other than comments.
> 
> P.P.S.  I did try running some more test commands, just to ses if I could
> maybe figure out what's going wrong here.  Output for those is/was as follows:
> 
>    % avahi-resolve-host-name bromance
>    Failed to create host name resolver: Invalid host name
>    % avahi-resolve-host-name BRN001BA9A2273F.local
>    Failed to resolve host name 'BRN001BA9A2273F.local': Timeout reached
>    % avahi-resolve-host-name bromance.local
>    Failed to resolve host name 'bromance.local': Timeout reached
>    % avahi-resolve-host-name BRN001BA9A2273F
>    Failed to create host name resolver: Invalid host name
> 
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