OT: Windows serial port sniffing
koder
hmichels01 at earthlink.net
Mon Aug 18 14:40:15 MST 2008
Sorry for the delay, but I had a meeting to attend.
Eric is absolutely correct about the need for a voltage divider.
You will need to determine that the output of your system is not ging to
overwhelm things.
The article I had in mind is calling for an 1/11 divider.
Electronic Circuits for the Evil Genius by Dave Cutcher
http://www.books.mcgraw-hill.com/authors/cutcher
There you will find the Windoze program Winscope 2.51
The black wire will go from your ground to the base portion of the audio
plug. Use a 100 ohm resister to bridge the black wire to the red wire
which goes to the tip.
>From the junction of the red wire and the 10 ohm resister connect a 1000
ohm resister. The other end of the resister goes to your connection.
I accept no responsibility for any damage to equipment for any
miscommunication regarding the construction of this circuit.
Cutcher says your sound card will not take more than two volts.
The divider will drop a nine volt signal to .8 volts.
I no longer have a Win machine so I have not been able to use this
circuit. I hope someday to write such a program in Linux, but if someone
else gets there first it will not break my heart
Harold
-----Original Message-----
From: Eric Cope <eric.cope at gmail.com>
Reply-To: Main PLUG discussion list
<plug-discuss at lists.plug.phoenix.az.us>
To: iscreamkid at gmail.com, Main PLUG discussion list
<plug-discuss at lists.plug.phoenix.az.us>
Subject: Re: OT: Windows serial port sniffing
Date: Mon, 18 Aug 2008 10:50:02 -0700
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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