Using Raspberry Pi as scan server?

[lewisbolaton]

I was wondering whether I could use this package in a Raspberry Pi (Raspbian OS) for creating a wireless scan server. I have an HP Deskjet Ink Advantage 1515 printer/scanner and it doesn't have a built-in network support. I am now using this Raspberry Pi as a wireless print server using CUPS but I wanted to extend its feature to wireless scanning.

Additional question: How is this package different from SimulPiscator/AirSane besides the web-interface?

[alexpevzner]

The sane-airscan is a scanner driver for SANE, not the server.

If your printer supports IPP-over-USB protocol, you may try to use ipp-usb (https://github.com/OpenPrinting/ipp-usb) to re-export it to the network. Regardless of its name, IPP-over-USB typically exposes printing, scanning and device's web console.

To check if IPP-over-USB is supported by device, do lsusb -v as root, find your printer's entry and look for the following lines:

      bInterfaceClass         7 Printer
      bInterfaceSubClass      1 Printer
      bInterfaceProtocol      4

If you see combination of Class=7 and Protocol=4, your device supports IPP-over-USB.

The ipp-usb daemon by default doesn't expose devices to the network, only to localhost. To change this behaviour, edit /etc/ipp-usb/ipp-usb.conf, find the following line in the [network] section:

[network]
  interface = loopback

And replace loopback with all.

If it works for you, your printer will appear on a network as an IPP printer and eSCL scanner, and no additional software on the Raspberry Pi side will be needed (no CUPS etc).

The AirSane program does an opposite to sane-airscan task: it converts any SANE-compatible scanner into the eSCL server. If you will use AirSane, you'll probably will need sane-airscan on a client side, because sane-escl driver, included into the sane-backends package doesn't work with AirSane (at least, it didn't some time ago). And you will need to run CUPS on your Raspberry Pi to export printing parf of your device.

My recommendation: use ipp-usb, if your printer is supported by this program, otherwise fall back to AirSane or even saned (comes with SANE)

[lewisbolaton]

So I checked with my current setup and it seems that only the bInterfaceProtocol is different. I had the following relevant lines after running lsusb -v as a superuser:

bInterfaceClass       7 Printer
bInterfaceSubClass    1 Printer
bInterfaceProtocol    2 Bidirectional

Does this mean I cannot use ipp-usb? Does the value of bInterfaceProtocol has something to do with the CUPS server I already set up and hplip? I used lsusb while the relevant CUPS packages are still installed and running, will removing those change the value of bInterfaceProtocol?

If I use AirSane instead, will Apple devices detect the scanner automatically or do I still need to install an additional app? I think Fedora, the distribution I use, already includes sane-airscan natively so I can technically run GNOME Document Scanner and it will automatically search then detect the scanner too. Is my assumption correct?

Edit: Had an additional question

[alexpevzner]

There may be multiple lines per device, but if none of them contains 7/4 combination, yes, it means that you can't use ipp-usb with this device.

These numbers are hardwired into the device, and software installed and running on the host can't change them.

[lewisbolaton]

Thank you for your prompt response. I edited my previous reply with an additional question. I hope you can also address it too.

[alexpevzner]

If I use AirSane instead, will Apple devices detect the scanner automatically or do I still need to install an additional app?

I don't know. AirSane author claims so, but I briefly tested with Mopria for Android (it also uses eSCL), and didn't succeed. It may be my mistake though, I didn't investigate thoroughly. But ipp-usb on a same machine works well with Mopria.

I think Fedora, the distribution I use, already includes sane-airscan natively

Yes, starting from Fedora 32

so I can technically run GNOME Document Scanner and it will automatically search then detect the scanner too. Is my assumption correct?

Yes

[markosjal]

I am working on a project currently to share a windows scanner by way of eSCL. Once I get through that , it is my intention to make the SANE to eSCL equivalent for Linux.

I have tested the Airsane package with mixed results .if I felt it were up to par, I would not bother with my own. Unfortunately with Airsane I have seen client incompatibility as well as some scanners being incompatible. I do not see it improving rapidly.

I will say after playing with eSCL for a couple years now that building an eSCL server is much more complex than the client.