Network backend improvements

[vulpes2]

Support for two-way communication and discovery (via SNMP) would be good to have at some point.
There is an existing PR in the original repo that may be worth looking into: pklaus#137

[matmair]

The current network backend seems half finished, and discovery would also be very interesting for inventree-brother-plugin

[matmair]

pklaus#137 look interesting but seems to introduce pysnmp as a dependency. Would be cool if that dependency could be optional

[vulpes2]

I looked into this and it's not an easy fix. The network backend is not half-finished, Brother doesn't support bidirectional comms through the raw network socket (port 9100) at all. The printer will only send back an error status when the buffer is full, but otherwise it won't respond to anything.

There are two channels that we can get stats from the printer with: IPP and SNMP. Both are kind of annoying to support and neither can be used for printing within the scope of this library (only URF is accepted over IPP on these printers). So basically you need to pick either IPP or SNMP, both would require a new dependency.