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ETHERNET PRINT SERVER
not support all the data-processing options that the printer interface does.
It cannot be configured to generate a banner page, for example, or
perform tab expansion. The options for the printer-interface method are
not valid with the device interface method.
The setup for the two RTEL methods is similar, but not identical. Both
methods take advantage of the “server_hosts” file to read configuration
information. This file shows the host’s print queues and devices, and controls
which service/port and server connections will map to. It is also used to
specify options for processing the data sent to the EPS. For example, you can
add a banner page to a particular print queue. In the case of device files,
options to the rteld command line can also be specified in the “server_hosts”
file.
To use the printer-backend method, you must run a shell script (mkprt)
that will add a new printer queue on the host and link any executables RTEL
needs to start RTEL connections. The script can also add new entries to the
“server_hosts” file if you desire. For lpr-style printers, the host’s /etc/printcap
file can be updated by mkprt. Mkprt will also offer to add your EPS’ IP
address to the host table (/etc/hosts) if it is not there already. You can enter
addresses to these files by hand instead of automatically, if desired. You need
to configure the EPS separately (for service and/or port setups). After these
2 steps, you can use the EPS as a print device from the host, and it will
support queued jobs, etc.
Using the device-file interface involves less initial setup, but is potentially
more complicated for multiple devices. It does allow more flexibility and
functionality than the printer-backend method. To setup the device
interface, you must run the rteld program for each device desired. In
general, the rteld program allocates a pseudo-tty device pair and attempts to
connect them to the specified EPS and service. Once the program creates
this pair, any user or application can use the tty device as a connection to the
EPS. Applications can then print directly to the device, users can echo data to
the connection, and communications programs can use the device as if it was
a physical device on the host. See the rteld man page in the RTEL/source
distribution directory for a detailed list of available rteld options.
There are 2 main executables that are used for the RTEL handling:
1. The lp_filter and lpr_filter programs are backend filters for your host’s lp
or lpr print spooler. When using the print queue interface, the EPS calls
these programs to actually connect to the EPS and output the job to a
serial port. They can also be configured to do limited data processing,
such as tab expansion.
2. The rteld program is run whenever a device interface to an EPS service
is created, used, or deleted. It can also be run at system startup time to
establish any “permanent” pseudo-device connections.