During a telnet session to an HP JetDirect card using the printer's IP address / port 9100, commands such as:
@PJL INFO STATUS
are entered which get back
CODE=10001
DISPLAY="00 READY"
ONLINE=TRUE
But when the printer is taken off line there is no response to the PJL command. There is also no response to the PJL command when a paper jam is reported from the printer's display. The goal is to write a script to determine if the printer has stopped printing because it is done or for other reasons such as a paper jam or an empty paper tray. In the former case power will be cut to the printer. But in the latter cases power will remain on so the situation can be resolved.