Automatic discovery of printers not working about androidcupsprint

[BenoitDuffez]

Do you use avahi/mDNS?

[gerroon]

Hi

I am not sure. Do you mean on Android or Linux? I did not anythign special myself, all the server printer stuff is as is.

[BenoitDuffez]

I mean on the (Linux) server. This enables auto-discovery of printers.

For the search button for manual "discovery", I haven't tested this lately so it may not work. I'll definitely test this.

[dueringa]

Not sure if this is the same issue, but if I enter the hostname manually in the "add printers" view, and click the search button (https://github.com/BenoitDuffez/AndroidCupsPrint/blob/master/app/src/main/res/layout/add_printers.xml#L20), nothing happens. I don't see anything relevant in the logcat either.

If I enter nothing in the field and click the button, I get
04-14 17:36:36.941 26470 26584 W System.err: java.net.UnknownHostException: http://:631/printers/ (which I expected).

Entering http://<host>:631/printers/ in my browser on my PC shows me the CUPS web page with the printers on this host. Sharing is enabled for the relevant printer.

On the other hand:
In the "main view" (Settings -> Print -> Android CUPS print) I get a logcat message
04-14 17:42:28.967 26470 27018 V CUPS : No answer in mDNS response: java.net.DatagramPacket@66d1f9b

[BenoitDuffez]

You need to type an IP address / host name there. Then the app will try to scan that host for printers.

If you don't want to type anything you need to use mDNS.

[dueringa]

Regarding the automatic configuration, I activated the avahi service on my Raspberry Pi, where CUPS is running (and the printer is connected). The printer was found.

The search for printers on the entered host, however, didn't return any results. I guess I'll install Android Studio in the course of the next days and try to debug it to find out what goes wrong.

[BenoitDuffez]

Yeah that feature is flaky at best. I think that mDNS is so good that only it should be used. I didn't test the scan host feature to be honest.
I'd be glad to accept your contributions though!

[532910]

Automatic discovery of printers not working still not working!

I have correct setup. Linux client successfully discovers cups server with no cups* packages, only avahi-daemon.

That time I switch "Android CUPS Print" service in "Printing" settings I got in logcat:

V CUPS : No answer in mDNS response: java.net.DatagramPacket@186e79d
V CUPS : No answer in mDNS response: java.net.DatagramPacket@170a412
D CUPS : onPrintersDiscovered({})

but "tcpdump -vni br-lan udp and port 5353" show answers:

10.8.8.4 - phone
10.8.8.1 - cups server with avahi-daemon
10.8.8.6 - printer, accessible only from 10.8.8.1, 10.8.8.4 doesn't see it

IP 10.8.8.4.5353 > 224.0.0.251.5353: 0 PTR (QM)? _ipp._tcp.local. (33)
IP 10.8.8.6.5353 > 224.0.0.251.5353: 0*- [0q] 1/0/5 PTR Samsung ML-2160 Series (SEC001599E1EEE9)._ipp._tcp.local. (654)
IP 10.8.8.1.5353 > 224.0.0.251.5353: 0*- [0q] 5/0/0 PTR Samsung ML-2160 Series @ roo._ipp._tcp.local., (Cache flush) TXT "txtvers=1" "qtotal=1" "rp=printers/printer" "ty=Samsung ML-2165, 2.0.0" "adminurl=https://roo.local:631/printers/printer" "priority=0" "product=(ML-2165)" "pdl=application/octet-stream,application/pdf,application/postscript,image/jpeg,image/png,image/pwg-raster,image/urf" "URF=DM3" "UUID=3154c96e-9ce7-33ae-6523-7381f61a1601" "TLS=1.2" "Duplex=T" "Copies=T" "printer-state=3" "printer-type=0x3056", (Cache flush) SRV roo.local.:631 0 0, (Cache flush) AAAA fe80::20d:b9ff:fe4a:f806, (Cache flush) A 10.8.8.1 (520)
IP 10.8.8.4.5353 > 224.0.0.251.5353: 0 PTR (QM)? _ipps._tcp.local. (34)
IP 10.8.8.1.5353 > 224.0.0.251.5353: 0*- [0q] 5/0/0 PTR Samsung ML-2160 Series @ roo._ipps._tcp.local., (Cache flush) TXT "txtvers=1" "qtotal=1" "rp=printers/printer" "ty=Samsung ML-2165, 2.0.0" "adminurl=https://roo.local:631/printers/printer" "priority=0" "product=(ML-2165)" "pdl=application/octet-stream,application/pdf,application/postscript,image/jpeg,image/png,image/pwg-raster,image/urf" "URF=DM3" "UUID=3154c96e-9ce7-33ae-6523-7381f61a1601" "TLS=1.2" "Duplex=T" "Copies=T" "printer-state=3" "printer-type=0x3056", (Cache flush) SRV roo.local.:631 0 0, (Cache flush) AAAA fe80::20d:b9ff:fe4a:f806, (Cache flush) A 10.8.8.1 (521)

When I add printer manually by https://roo.local:631/printers/printer or http://roo.local:631/printers/printer all works fine.

[BenoitDuffez]

Is this still active? I've been using mDNS for years and it's working like a charm, and I haven't got so many feedback about this issue. I'm tempted to close this.

[532910]

Yes, this is still active!
I can make a qemu/virtualbox image with cups and avahi.

[532910]

BTW, "Default Print Service" from the lineageos 15.1 sucessfully founds the printer.

[BenoitDuffez]

Gah. Sorry but I don't like lineage. I've used it on a very old device to get a more recent version of Android, and it breaks a lot of internal APIs. I'm afraid I won't be providing support on non-stock versions.

[BenoitDuffez]

Have you reproduced this on recent beta builds? If you have the Play Store, please reproduce on the version that will be released tomorrow, and post logs here. If you don't have the Play Store, please compile an apk from the latest commit in develop and post logs. Thanks

[532910]

ok, I'll test it again within a week

[BenoitDuffez]

Please let me know whether this can be closed.

[532910]

Sorry for late response. I still experience this issue. I'll do more tests for research.

[532910]

I've done more tests for research and now I don't experience this issue more (:
The main change was an upgrade from debian stretch to buster (cups 2.2.1-8+deb9u3 -> 2.2.10-6, avahi-daemon 0.6.32-2 -> 0.7-4+b1)

[532910]

So it can be closed.