OT: Windows serial port sniffing

[Eric Cope]

be careful at connecting serial wires +-15v to audio inputs... Unless you
know what a voltage divider is...
A divide by 10 sounds correct, but I am not sure...
http://www.physicsforums.com/showthread.php?t=131827

I recall being able to control some of the handshake wires in a serial
connection in a windows program in a manner that you describe, but that was
a few years ago... There should be some tutorials on Google...

http://msdn.microsoft.com/en-us/library/ms810467.aspx

Good luck,
Eric

On Mon, Aug 18, 2008 at 10:39 AM, koder <hmichels01 at earthlink.net> wrote:

> There is a program which I am pretty sure is free that will look at the
> voltage levels on the serial port and display them as a graphic display.
> it was intended to allow you to use the serial port as a voltmeter.
>
> The program is made available by the man who writes the Evil Genius
> series of hardware books.
>
> I am not able to give more information at this time.
>
> What you do is run a wire across a resister that drops the voltage to
> audio levels. Plug the wire into the line in on your sound card. The
> program seed the analog signal and displays it on the graph.
>
> Harold
>
> -----Original Message-----
> From: Charles Jones <charles.jones at ciscolearning.org>
> Reply-To: Main PLUG discussion list
> <plug-discuss at lists.plug.phoenix.az.us>
> To: plu >> Main PLUG discussion list
> <plug-discuss at lists.plug.phoenix.az.us>
> Subject: OT: Windows serial port sniffing
> Date: Mon, 18 Aug 2008 08:46:49 -0700
>
> This is technically a windows question, but I thought I would ask here
> anyway, because many of us were hacking before MS-windows existed, and
> also ran various versions of MS-windows in our time (which is why we
> love Linux so much now!) and have dealt with serial ports from dealing
> with modems and the like. I figured I would tell you all about a minor
> problem I am thinking of tackling, and see if you had any suggestions.
>
> I'm dealing with an RFID badge-access system that uses windows-based
> administration software. Basically some software that runs on windows,
> using an mssql db, and communicates with the hardware via the serial port.
>
> The software has a function to send a timed pulse to unlock a door(s)
> for X number of seconds.  I'm looking for a way to do the same thing,
> but from another machine so that I can use a script or even a CGI to
> control the door. Yes, I realize this opens us up to someone "hacking"
> their way into the office, but we also have a security system and if
> they have root on our servers then we have bigger problems :)  I digress...
>
> I have some long ago experience in serial port programming. In school I
> wrote a voicemail system in Turbo Pascal (heh), that controlled a POTS
> line via a relay that I connected to the serial port. I remember
> studying the serial port pinouts and figuring out how to control the
> voltage level to each of the pins.
>
> That being said, I have several things I have to consider:
> * Is the door lock pulse simply a voltage level sent to the serial port,
> or is there some sort of protocol (an actual serial connection) between
> the computer and the hardware?
> * Is the signal being sent just a toggle, or a specific turn on/off events?
>
> I basically need a way to snoop the serial port to see what is being
> sent, but I'm not sure of the best way to do it.  If it is just voltage
> levels being sent to the hardware, I could do it with just a multimeter
> and figure out which pins it is activating.  However, if there is an
> actual serial connection (null modem or something) going on, it will be
> much more difficult to observe what data is being sent. I think also you
> can purchase an in-line dongle that has LEDs that will show the status
> of the data lines.
>
> I suppose one of the first things I could do is to just unplug the
> serial port, and try to use any functions that talk to the hardware.  If
> there is any data connection required, it should complain that it is not
> connected.
>
> Theoretically I could write a small a small C++, (or even Win32 perl)
> daemon that would run on the winblows machine and provide a way to
> toggle the lock/unlock signal via a TCPIP connection. I may run into a
> snag where, if I remember correctly, if something has control of a
> serial port in Windows, no other process can open it.  Maybe I could do
> something sneaky like a Y-adapter and just send the signal from another
> machine altogether. I wonder if I would have to use some diodes to keep
> any voltage from one leg of the Y from traveling back to the other
> machines serial port...hmmm
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