Novell LINUX ENTERPRISE SERVER 10 SP2 - INSTALLATION AND ADMINISTRATION Installation Manual page 477

The following command can be used to test if a TCP connection can be established
to cupsd (port 631) on host:
netcat -z host 631 && echo ok || echo failed
If the connection to cupsd cannot be established, cupsd may not be active or
there may be basic network problems. lpstat -h host -l -t returns a
(possibly very long) status report for all queues on host, provided the respective
cupsd is active and the host accepts queries.
The next command can be used to test if the queue on host accepts a print job
consisting of a single carriage-return character. Nothing should be printed. Possibly,
a blank page may be ejected.
echo -en "\r" \
| lp -d queue -h host
Troubleshooting a Network Printer or Print Server Box
Spoolers running in a print server box sometimes cause problems when they have
to deal with a lot of print jobs. Because this is caused by the spooler in the print
server box, there is nothing you can do about it. As a work-around, circumvent the
spooler in the print server box by addressing the printer connected to the print
server box directly with TCP socket. See Section 23.5, "Network Printers"
(page 447).
In this way, the print server box is reduced to a converter between the various forms
of data transfer (TCP/IP network and local printer connection). To use this method,
you need to know the TCP port on the print server box. If the printer is connected
to the print server box and powered on, this TCP port can usually be determined
with the nmap utility from the nmap package some time after the print server box
is powered on. For example, nmap IP-address may deliver the following
output for a print server box:
Port State
23/tcp open
80/tcp open
515/tcp open
631/tcp open
9100/tcp open
This output indicates that the printer connected to the print server box can be ad-
dressed via TCP socket on port 9100. By default, nmap only checks a number of
commonly known ports listed in /usr/share/nmap/nmap-services. To
Service
telnet
http
printer
cups
jetdirect
Printer Operation 459