[BusyBox] Pass Thru Echo In Telnet Client

[Christopher M. Williams]

On Tue, 2004-05-25 at 21:17, Rob Landley wrote:
> On Friday 21 May 2004 15:58, Christopher Williams wrote:
> > Hello,
> >
> > I have hacked away at networking/telnet.c to add support for ansi/vt100
> > pass-through printing. It's an ugly hack, only a few lines of code, but
> > I wanted to see how much interest there was in cleaning it up to merge
> > or simply offer as a patch. I chose Busybox because the terminals are
> > diskless 386 PCs with 4MB of ram booting GNU/Linux over BOOTP and using
> > NFSROOT. Other terminal emulators had pass-through but used too much
> > ram, and we were already using Busybox as our telnet client.
> 
> Could you explain to me how this differs from netcat?
> 
> Rob

Rob,

Please excuse my ignorance of netcat, I'm not very familar with it. I
perused the current home page to refresh my memory. Netcat seems to be a
far more generic tool for reading or writing to TCP/UDP sockets. What I
needed was classic ansi/vt100 pass-through printing support via the
terminal emulator. Essentially the user interacts with terminal software
and as part of the output from the server the escape code ^]]4i turns on
echo to printer, and ^]]5i turns off echo to printer. In this case we
are redirecting the printer to the modem to autodial for polling staff.
It's also commonly used to print invoices, orders, etc from terminal
emulators to the local printer from legacy applications where the
printer is attached to a dumb terminal versus networked printing via
lpd. The main purpose is to work with existing terminal applications
that write ^[[4i...data to print...^[[5i or ^[[4i...AT modem
command...^[[5i. Netcat looks like it would require modifying the server
app so that data to be echoed to printer or modem would be written to a
listener daemon on some other port, rather than part of the telnet
session TCP stream. The requirements here are:
 1) compatibility with existing UNIX line-of-business interactive
application on the server side which sends 'log to printer' vt100 codes
as part of terminal session to client terminal
 2) low overhead on diskless 486 clients

I wasn't aware that Netcat could be used for terminal emulation, if it
has such a mode and it has a smaller footprint, I'll take another look
at it.

Best Regards,
Chris

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