Operation Manual

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. Possi-
bly, 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 multiple print jobs. Since this is caused by the spooler in the print
server box, there no way to resolve this issue. As a work-around, circumvent the
spooler in the print server box by addressing the printer connected to the print
server box directly with the TCP socket. See Section 14.5, “Network Printers”
(page 168).
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 turned 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 up. For example, nmap IP-address may deliver the following
output for a print server box:
Port State Service
23/tcp open telnet
80/tcp open http
515/tcp open printer
631/tcp open cups
9100/tcp open jetdirect
This output indicates that the printer connected to the print server box can be
addressed 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 check all
possible ports, use the command nmap -p from_port - to_port IP-address . This
may take some time. For further information, refer to the man page of nmap.
Enter a command like
echo -en "\rHello\r\f" | netcat -w 1 IP-address port
cat file | netcat -w 1 IP-address port
Printer Operation 175