Using Xmodem without a login

John Gayman john at wa3wbu.UUCP
Mon Aug 13 01:55:35 AEST 1990


   I'm having some diffculty which I beleive someone on the Net can probably
shed some light on. I'm trying to communicate with a bar-code machine on
a serial port. The configuraation is very simply. I have a SVr2 machine
hooked to the bar-code device at 9600 baud running through a pair of
short haul modems. Distance is about 1000 feet. 

   At the moment I'm using "dd" to collect data from the barcode unit like
"dd if=/dev/ttyXX of=data". This works ok. Also I send data to the remote
site to be printed by simply "catting" a data file and redirecting it
to the appropriate serial port. The files I'm sending back and forth are
relatively small, text files. 

   The problem is that these files are going to get bigger. By simply
sending data streams I am extremely subseptable to noise and data
corruption. The barcode unit support Xmodem transfer. I cannot think
of anyway in my transfer shell script to implement a xmodem transfer
remotely without having a logged-in station request it. The xmodem
programs I've been playing with seen to work for a PC being logged in as
a terminal, they kick off something like "xmodem -sb filename", hit
the PC programs download key and away it goes. Is there anyway to
tell it basically "start Xmodem transfer of fileA out port tty00"
and away it goes ?

   Assuming this procedure is more trouble than its worth, maybe there
is another avenue. Would replacing my short-haul modems with a pair
of MNP-type modems (dedicated line) allow me to continue using my
simple "dd" and "cat" transfer method yet make it error correcting ?
I have no experience with MNP modems but the way I understand it they
provide an error-free (so to speak) link between a terminal and a 
host. Do you think they would better serve my needs.

   I hope I've done an adaquate job explaining my situation so that
someone can offer suggestions. If I've left something out, please drop
me a note and I'll try and fill you in. Thanks much!




						John


-- 
John Gayman, WA3WBU              |           UUCP: uunet!wa3wbu!john
1869 Valley Rd.                  |             
Marysville, PA 17053             |           Packet: WA3WBU @ WB3EAH 



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