Intercept serial port communication

Posted on 2001-08-06
Last Modified: 2013-11-15

Because I want to understand the protocol in which an application "talks" to external hardware, I need to have a program which intercepts the "talking" and dumps it to a file.

The program must sit and wait until another program writes or retrieves data to or from the COM1: port (it has to run on a Windows 2000 machine).

Is this possible in VISUAL C++ (or in any way at all?). If such a program already exists, please say where I can get it!

Thnx in advance,

Bart van der Vliet
Question by:trance_creator
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LVL 86

Expert Comment

ID: 6356018
>>Is this possible in VISUAL C++ (or in any way at all?).

You can always do that usina API hooking - see and on this issue.

BTW: A great tool that already does what you want to is

Expert Comment

ID: 6356084
You have to use following APIs CreateFile & ReadFile to Read from ComPort.
Do you only want to Read from it?
LVL 86

Expert Comment

ID: 6356140
>>You have to use following APIs CreateFile & ReadFile to
>>Read from ComPort.

But these APIs don't allow to intercept an ongoing communication...
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Expert Comment

ID: 6356174
oh yes, thats right
okay, want to know what i did?
i had to monitor the communication over COM1 Port.
I made a patch-cable that was 1:1:1, that means APLLICATION - COM1 - COM2

over COM1 i communicated with the APPLICATION and on COM2 i watched what's happening. I think that's a very easy and fast way to do that...
U can watch COM2 with a normal Terminal-Program like Windows Hyper Terminal...
LVL 86

Accepted Solution

jkr earned 250 total points
ID: 6356191
>>okay, want to know what i did?

Well, that works - but it's easier to use 

Expert Comment

ID: 6356247
that's maybe right...but you're a little restricted with that application...
but anyway, maybe it's enough for trance_creator...

grEEz RideOn

Author Comment

ID: 6358384
The program is exactly what I need! Thanks a lot!!!


Bart van der Vliet

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