[sane-devel] Net Client Not Contacting Server

Ralph Little skelband at gmail.com
Wed Sep 9 19:41:56 BST 2020

OK, no we're getting somewhere.

On Wed, Sep 9, 2020 at 10:29 AM C. Cook <c.a.cook at quantum-sci.com> wrote:

> ...
I didn't see any traffic when not specifying the interface, so apparently
> in that case lo is ignored.  But now I see attempts.
> I changed net.conf to instead of localhost and:
> # SANE_DEBUG_NET=128 scanimage -L
> [sanei_debug] Setting debug level of net to 128.
> [net] sane_init: authorize != null, version_code != null
> [net] sane_init: SANE net backend version 1.0.14 (AF-indep+IPv6) from
> sane-backends 1.0.27
> [net] sane_init: Client has little endian byte order
> [net] sane_init: searching for config file
> [net] sane_init: connect timeout set to 30 seconds
> [net] sane_init: trying to add scan-server
> [net] add_device: adding backend scan-server
> [net] add_device: error while getting address of host scan-server: Name or
> service not known
> [net] sane_init: trying to add
> [net] add_device: adding backend
> [net] add_device: backend added
> [net] sane_init: done reading config
> [net] sane_init: evaluating environment variable SANE_NET_HOSTS
> [net] sane_init: evaluating environment variable SANE_NET_TIMEOUT
> [net] sane_init: done
> [net] sane_get_devices: local_only = 0
> [net] connect_dev: trying to connect to
> [net] connect_dev: [0] connection succeeded (IPv4)
> [net] connect_dev: sanei_w_init
> [net] connect_dev: net_init (user=carl, local version=1.0.3)
> [net] connect_dev: freeing init reply (status=Success, remote
> version=1.0.3)
> [net] connect_dev: done
> [net] sane_get_devices: finished (0 devices)
> No scanners were identified. If you were expecting something different,
> check that the scanner is plugged in, turned on and detected by the
> sane-find-scanner tool (if appropriate). Please read the documentation
> which came with this software (README, FAQ, manpages).
> [net] sane_exit: exiting
> [net] sane_exit: closing dev 0x55f2484331e0, ctl=3
> [net] sane_exit: finished.
No need to worry about SANE_NET_HOSTS now, we are seeing activity.
So it looks like the net backend is connecting to saned at the server end.
I have not used reverse SSH before so I had to look that up. Interesting.

Seems like we need to look to the server end now.
So, let's review what we have there.
saned is effectively just another SANE frontend. It connects to the
backends in exactly the same way that scanimage and xane do.

On the server, could you try scanimage -L there and post what you get?
Hopefully, you should see the scanner listed.
If so, then we need to discover why saned does not. I would be thinking
about the user that saned is running as, therefore its permissions and the
If not, then we have some problems with the driver setup and we can take it
from there.

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