RE: tcpdump equivalent for the serial port

["Mariano Moreyra" <moremari@aca.org.ar>]

I'm using that cable between a PC and a Fiscal Printer, but it's a RS232
link...
We didn't have any problem with signal variations. But I understand that
with an RS422 link you could have more problems.
Wish I could help you, but I don't know how to write a software to do this
kind of sniffing.


-----Mensaje original-----
De: Nicolae Mihalache [mailto:mache@abcpages.com]
Enviado el: Viernes, 12 de Septiembre de 2003 11:02
Para: mariano_moreyra@aca.org.ar; linux-c-programming@vger.kernel.org
Asunto: Re: tcpdump equivalent for the serial port


Mariano Moreyra wrote:

>Hi Nicolae,
>
Hi Mariano!

>I think that what you want to do is not posible just with a software.
>You have to build a special cable to do that (somebody tell me if I'm
wrong,
>or if knows another option)
>In my job we have one of those cables because we needed to see what was
>going on between two applications that talk to each other via serial port.
>The bad thing is that you need a third computer that would be the sniffer.
>
The problem is that opening the cable and connecting it to a third port
may introduce some variations in the signals going over the serial
cable. This is something that I want to avoid as much as possible. The
other end of the serial cable is not another computer but a device that
is itself the subject of development and test so it can not be assumed
as working nor it can be developed with a non-nominal serial cable
connected to it. Even worse, my serial link is not RS232 but RS422 which
has a higher speed and it's more difficult to have break-out capability
without interferences.
This is why I'm looking for a software solution, i.e. something that
communicates with the serial driver and gets all the messages that pass
through it.

Nicolae