7.6.3. Networked Printing

FreeBSD supports networked printing: sending jobs to remote printers. Networked printing generally refers to two different things:

• Accessing a printer attached to a remote host. You install a printer that has a conventional serial or parallel interface on one host. Then, you set up LPD to enable access to the printer from other hosts on the network. Section Printers Installed on Remote Hosts tells how to do this.

• Accessing a printer attached directly to a network. The printer has a network interface in addition (or in place of) a more conventional serial or parallel interface. Such a printer might work as follows:
  • It might understand the LPD protocol and can even queue jobs from remote hosts. In this case, it acts just like a regular host running LPD. Follow the same procedure in section Printers Installed on Remote Hosts to set up such a printer.

  • It might support a data stream network connection. In this case, you ``attach'' the printer to one host on the network by making that host responsible for spooling jobs and sending them to the printer. Section Printers with Networked Data Stream Interfaces gives some suggestions on installing such printers.

7.6.3.1. Printers Installed on Remote Hosts

The LPD spooling system has built-in support for sending jobs to other hosts also running LPD (or are compatible with LPD). This feature enables you to install a printer on one host and make it accessible from other hosts. It also works with printers that have network interfaces that understand the LPD protocol.

To enable this kind of remote printing, first install a printer on one host, the printer host, using the simple printer setup described in Simple Printer Setup . Do any advanced setup in Advanced Printer Setup that you need. Make sure to test the printer and see if it works with the features of LPD you've enabled.

If you're using a printer with a network interface that's compatible with LPD, then the printer host in the discussion below is the printer itself, and the printer name is the name you configured for the printer. See the documentation that accompanied your printer and/or printer-network interface.

Then, on the other hosts you want to have access to the printer, make an entry in their /etc/printcap files with the following:

1. Name the entry anything you want. For simplicity, though, you probably want to use the same name and aliases as on the printer host.

2. Leave the lp capability blank, explicitly (:lp=:).

3. Make a spooling directory and specify its location in the sd capability. LPD will store jobs here before they get sent to the printer host.

4. Place the name of the printer host in the rm capability.

5. Place the printer name on the printer host in the rp capability.

Here's an example. The host rose has two printers, bamboo and rattan. We'll enable users on the host orchid to print to those printers. Here's the /etc/printcap file for orchid (back from section Enabling Header Pages ). It already had the entry for the printer teak; we've added entries for the two printers on the host rose:

#
#  /etc/printcap for host orchid - added (remote) printers on rose
#

#
#  teak is local; it's connected directly to orchid:
#
teak|hp|laserjet|Hewlett Packard LaserJet 3Si:\
	:lp=/dev/lpt0:sd=/var/spool/lpd/teak:mx#0:\
	:if=/usr/local/libexec/ifhp:\
	:vf=/usr/local/libexec/vfhp:\
	:of=/usr/local/libexec/ofhp:

#
#  rattan is connected to rose; send jobs for rattan to rose:
#
rattan|line|diablo|lp|Diablo 630 Line Printer:\
	:lp=:rm=rose:rp=rattan:sd=/var/spool/lpd/rattan:

#
#  bamboo is connected to rose as well:
#
bamboo|ps|PS|S|panasonic|Panasonic KX-P4455 PostScript v51.4:\
	:lp=:rm=rose:rp=bamboo:sd=/var/spool/lpd/bamboo:

mkdir -p /var/spool/lpd/rattan /var/spool/lpd/bamboo
chmod 770 /var/spool/lpd/rattan /var/spool/lpd/bamboo
chown daemon.daemon /var/spool/lpd/rattan /var/spool/lpd/bamboo

Now, users on orchid can print to rattan and bamboo. If, for example, a user on orchid typed

lpr -P bamboo -d sushi-review.dvi

7.6.3.2. Printers with Networked Data Stream Interfaces

Often, when you buy a network interface card for a printer, you can get two versions: one which emulates a spooler (the more expensive version), or one which just lets you send data to it as if you were using a serial or parallel port (the cheaper version). This section tells how to use the cheaper version. For the more expensive one, see the previous section Printers Installed on Remote Hosts .

The format of the /etc/printcap file lets you specify what serial or parallel interface to use, and (if you're using a serial interface), what baud rate, whether to use flow control, delays for tabs, conversion of newlines, and more. But there's no way to specify a connection to a printer that's listening on a TCP/IP or other network port.

To send data to a networked printer, you need to develop a communications program that can be called by the text and conversion filters. Here's one such example: the script netprint takes all data on standard input and sends it to a network-attached printer. We specify the hostname of the printer as the first argument and the port number to which to connect as the second argument to netprint. Note that this supports one-way communication only (FreeBSD to printer); many network printers support two-way communication, and you might want to take advantage of that (to get printer status, perform accounting, etc.).

#!/usr/bin/perl
#
#  netprint - Text filter for printer attached to network
#  Installed in /usr/local/libexec/netprint
#

$#ARGV eq 1 || die "Usage: $0 <printer-hostname> <port-number>";

$printer_host = $ARGV[0];
$printer_port = $ARGV[1];

require 'sys/socket.ph';

($ignore, $ignore, $protocol) = getprotobyname('tcp');
($ignore, $ignore, $ignore, $ignore, $address)
    = gethostbyname($printer_host);

$sockaddr = pack('S n a4 x8', &AF_INET, $printer_port, $address);

socket(PRINTER, &PF_INET, &SOCK_STREAM, $protocol)
    || die "Can't create TCP/IP stream socket: $!";
connect(PRINTER, $sockaddr) || die "Can't contact $printer_host: $!";
while (<STDIN>) { print PRINTER; }
exit 0;

#!/bin/sh
#
#  diablo-if-net - Text filter for Diablo printer `scrivener' listening
#  on port 5100.  Installed in /usr/local/libexec/diablo-if-net
#

exec /usr/libexec/lpr/lpf "$@" | /usr/local/libexec/netprint scrivener 5100