HP PCL/PJL reference - Printer Job Language Technical Reference Manual

11-20 Programming Tips for Using PJL EN
printer's response. The simplest solution for printer sharing boxes is
to forward all data received from the printer to all attached host
computers, and let the applications on each host computer ignore any
impertinent data, as described in the “Handling Unexpected Printer
Responses” section in this chapter.
The printer in this example is also attached directly to a network via a
network interface card installed into the printer's MIO interface.
Network servers #4 and #5 spool print jobs from network clients #6
and #7. In this example, the network clients can not interact directly
with the network-attached printer. The network spoolers can inject a
“print job” to query the printer and can expect to get responses back.
However, for this example, the network operating system does not
provide a mechanism which allows applications running on a network
client to query the printer and get a response.
The printer's I/O card, the printer sharing box, and the spoolers
running on the network servers can query the printer and expect to
receive a response since those components are connected directly to
the printer (i.e., no other printing system component except for the
communication cable is between the printer and those components).
In summary, an application running on host computer #1 can receive
printer responses if the operating system on the host computer
supports bi-directional communication over the serial I/O interface.
The application may have to wait for the printer's response if the
printer is processing a job from either the IEEE-1284-compatible I/O
interface or the MIO interface.
An application running on host computer #2 or #3 may receive printer
responses if the printer sharing box supports bi-directional printer
communication. However, since the printer sharing box does not have
enough information to route the response to the correct host
computer, the printer sharing box can forward all printer responses to
all attached host computers and let the application on the host
computer ignore any unneeded printer responses.
Applications on network clients #6 and #7 cannot receive any printer
responses due to the underlying network operating system. However,
the printer sharing box, the I/O card installed in the printer, and
spoolers running on network servers #4 and #5 can all query the
printer and expect a printer response (although the response will not
be immediate if the printer is processing a print job from a different I/O
interface).