Print Server Operation; Printer Queue - VSCOM netcom 123 User Manual

the local TCP Data Port as defined in the configuration of NetCom (see
5.1.2.2.5 and 5.3.3.2.5 above).
8.2. P S
RINT
Sometimes the NetCom Serial Device Servers are used together with
serial printers. These printers are available via a network to several
stations for printing. So far there have been two operation modes to
achieve this. First the serial port can operate as a TCP Raw Server, and
the station just sends the data to print via a TCP connection. As second
option a computer running Windows could install the driver for virtual
serial ports. The printer is then controlled via this Com port. In both
these solutions the buffering of data occurred on the client station.
Beginning with Firmware Version 2.2 the NetCom Devices offer a true
Print Server mode, using the Line Printer Daemon protocol as of
RFC1197. Here a print server (lpd) is a station with one IP Address and
a single defined port to accept commands and data for printing. Several
printers may be attached to the print server. Each printer has a separate
data queue for management of print jobs. The data of the jobs is saved
in this queue, instead of the client as before.
8.2.1. P
RINTER
The basic function of an lpd is to accept the data for printing, store it in
a spooler queue, and send it to the printer when this is ready for
printing. This is done for several queues in parallel. Each printer is
identified by the name of the queue, where it is attached to. The
NetCom Device Servers allow to configure a custom name for each
queue, while the default name is »lpd« plus the number of the serial
port (lpd1, lpd2, ...). This name is set in the properties of the serial port.
When the lpd is running on a separate computer, the hard disk is used to
save the data of the queues. The NetCom Servers neither have a mass
storage device, nor huge amounts of memory. Each queue accepts at
least one job with a size of up to 250 KB print data. If the job has more
data, memory is either assigned dynamically to save the job, or the data
is spooled through a ring buffer. Data is printed while the client still
sends data. The amount of available dynamic memory depends on the
number of ports in a NetCom Device Server, and the operations active
on these ports.
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