[cups] MacOS to Linux CUPS intermittent "printer not connected" problem

[Keith Oborn]

I’m running CUPS on a Raspberry Pi, drving a Kyocera laser, with a couple of Macs talking to it.

The Add Printer dialog on the Macs works fine: always sees the CUPS printer within seconds - tried removing and re-adding, and there is no real delay in seeing “printer at pi" as a Bonjour device.

When printing, however, both Macs regularly - but intermittently - show “printer is not connected” or “looking for printer” for arbitrarily long periods. They always print in the end. 

Sometimes a “pause. resume” on the Mac queue will fix it, sometimes not. A restart of CUPS on the Pi always seems to fix it.

This doesn’t seem to depend on recent print activity: sometimes multiple jobs are delivered immediately after the first, sometimes the first is delivered immediately and the second is delayed, sometimes the first is delayed, etc. I can see no pattern.