I share my scanner on the network using sane but after reloading my server I found it was not being seen from the network even though it appeared to be working locally.
I saw this kind of stuff in the logs:
Dec 19 15:56:19 localhost saned[32422]: saned (AF-indep+IPv6) from sane-backends 1.0.19 starting up
Dec 19 15:56:17 localhost saned[32422]: check_host: access by remote host: 10.0.0.55
Dec 19 15:56:17 localhost saned[32422]: init: access granted to saned-user@10.0.0.55
Dec 19 15:56:19 localhost saned[32422]: saned exiting
I increased the verbosity but it wasn't any more helpful:
[saned] check_host: access granted from IP address 10.0.0.55 (in subnet 10.0.0.0/24)
[saned] init: access granted
[saned] init: access granted to saned-user@::ffff:10.0.0.55
[saned] process_request: waiting for request
[saned] process_request: got request 1
[saned] process_request: waiting for request
[saned] process_request: got request 10
[saned] bailing out, waiting for children...
[saned] bail_out: all children exited
After much troubleshooting I realized that while local access worked file, saned was not working when running as user saned, but worked fine if run as root.
Obviously this looked like a permission problem, and it was. I checked the perms on the scanner device, /dev/sg2 and confirmed that saned had no access. But why? I checked the udev rules and found a rule that would give permissions to the scanner group, of which saned is a member. But this rule had set the permissions.
Then I realized that since I booted up with the scanner attached, and
then installed sane, the new udev rule would not have had any effect until the device was replugged or the system was rebooted. I restarted udev and un/re-plugged the scanner and then saned worked fine again!