Printers on Ethernet Terminal Servers

[Charles Hedrick]

We use Postscript printers on cisco terminal servers, fed by Adobe's
Transcript.  Some of them are fed from Pyramids.  We have modified
pscomm to be able to open a TCP connection directly to the terminal
server.  If you don't have the ability to open a TCP connection in
your printer filters, things get sort of messy, since lpd wants to
talk to /dev/somethingorother, and there's no obvious way to mknod a
TCP connection.  We have a hack called lp_pty that acts much like
telnet.  It opens a pty and a TCP connection, and passes bytes back
and forth.  If you run this, you can then point lpd at the tty
corresponding to the pty.  However in retrospect I suspect it would be
better to use the same approach that adobe does, which is to supply
filters (all of which are really links to the same script) that run a
program to handle output, and then make it open a TCP connection
directly.

Note that neither our hacked pscomm nor lp_pty is 100% reliable.  That
is, now and then you may have to abort the thing using lpc and
sometimes you have to do "clear line xxx" on the terminal server to
get things going again.  But I've never found hanging printers on
RS232 to be completely reliable, even with directly connected lines.
This doesn't seem to be any worse.