These packages are supported as part of the LPRng distribution.
The following are available:

ifhp - The Swiss Army Knife of Filters
   The recommended filter used for communication with HP PCL/PJL
   and Postscript printers.  Has many configuration options,  giving
   it extensive capability.
      - supports TCP/IP via JetDirect or print server interfaces
      - supports Tektronix Phaser,  QMS, HP, Lexmark, and
        other printers
      - LPRng compatible

lp_server
   causes a UNIX workstation to emulate (poorly, I admit) an HPJetDirect
   card so that you can make a connection directly to the serial/parallel
   port printer on the system.  You can also get FreeBSD on a Floppy
   and turn a 386 with 2 megabytes of memory and an NE2000 card into
   a LPRng server.

FILTERS_LPRng
   A collection of small and usually out of date filters for very
   special, whacko or legacy printers.

epson.html
   A handy reference for those hard to find epson printer control codes