Operation Manual

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 11.4, “Network Printers”
(page 152).
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 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
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
to send character strings or les directly to the respective port to test if the printer
can be addressed on this port.
162 Reference