If the spool queue destination is a remote printer supporting the Socket API, then you can have LPRng open a connection directly to the printer. These include the older Apple printers with TCP/IP support and the HP JetDirect supported printers.
The lp=server%port or lp=IPaddr%port format specifies that lpd should open a TCP/IP connection to the remote host and simply transfer verbatum the files to be printed.
The sh and sf will prevent lpd from trying to generate banner pages or put form feeds between jobs.
While this is the simplest printcap, it is also the most dangerous as there is nothing to prevent a malformed job from being sent to the printer. The next printcap example is much more robust:
# Simplest remote :lp=10.24.2.3%9100 :of=/usr/local/libexec/filters/ifhp :filter=/usr/local/libexec/filters/ifhp
This version will use the ifhp filter to precondition the printer and to process jobs. See ifhp Filter for details. The ifhp filter will perform the appropriate printer resets, translate job information, and ensure correct printer operation in the presence of errors. It will also produce voluminous error messages and status information.