Tracy Nelson on Sat, 18 Dec 1999 19:29:23 -0500 (EST)


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Re: [Plug] Plea for help - Strange Communications Protocol


Charles Stack wrote:
> I can dial in, and using V100 or ASCII emulation, I can log into the system.
> At that point, things get squirrly.  The data appears to be field oriented.
> Color attributes are sent (as is placement info), but as I enter data and
> leave each field, it is validate by the remote computer.  Oh yeah, the
> client software is also from IBM.

If you're using some client software, then there may be no official
protocol at all, just a convention used by the two pieces of software.
 
> The people who are running the system haven't a clue as to what protocol is
> being used (they just use it).  I have a 3270 emulator, but without an LU or
> IP address, it isn't doing me much good.

Do you have to set your modem up for bisync communications?  3270s are
"block" or "page mode" devices, and send data one screenful at a time. 
Since you're getting field-level remote validation, it's probably not
using a 3270 protocol.
 
> I'd even be happy with a good Linux based serial protocol analyzer that
> would allow me to view all traffic to/from the remote host and the client
> software.

It should be trivial to hack the serial port driver to log all traffic
to a file.  Set it to trap SIGUSR1 to toggle logging on and off.  You
can either have the logging function translate non-printing characters
to mnemonic sequences, or just log the raw data and dump it with od(1).

-- 
Just junk food for thought...

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