Solution:

When attempting to print to HP Print Servers (JetDirect) behind a firewall or when using NAT make sure the following ports are opened:

1. Port 9100 (HP Jetdirect) or when usign an HP JetDirect EX3 9101 for JetDirect port 2, and 9102 for JetDirect port 3.

2. Port 161 (SNMP) TCP & UDP.

If using the SCO Unix HP Network Printer (HPNP) the it uses SNMP to get the printer status before printing. If SNMP is unavailable it will not print. However, HPNP can be tricked. On your unspecified version of OSR5, rename the program /bin/getone to something else. If HPNP finds that it doesn’t have the proper binary to query the printer, it returns an always read message.