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54 CONFIGURING THE M208 FOR TCP/IP: Host Configuration
npd Pseudo-device Interface
The npd pseudo-tty daemon is used when bi-directional communications is required
between the printer and printing application, and when changes to the printer’s inter-
face script are undesirable.
Some applications like Sun NeWSprint and Adobe TranScript work best with a bi-
directional communications channel to the printer because they can provide more
details on the printer status. For example, PostScript printers can send error messages
back to the application as they occur. npd is used in this case making use of the TCP
protocol and pseudo-tty device drivers.
Figure 4: npd Overview
TCP/IP Host
M208
/dev/m208.prn
npd watches over this device
and sends any print jobs over
to the M208.
The spooler
processes the job
and passes it to the
printer device.
printer