sersniff 0.0.3 - A program to tunnel between 2 serial ports and show
what's happening.
Copyright 1999 Jonathan McDowell for Project Purple.
http://www.earth.li/projectpurple/progs/sersniff.html


Introduction:

This program was written to aid me with the decoding of the protocol
used by the Nokia 9000i Communicator to talk to the NServer software
Nokia provides, which only runs under Windows. Having hastily thrown
together the code to do what I needed it occured to me that others may
have a use for something similiar and that having a skeleton available
may help.

(Aside: Of course, in the usual tradition of Open Source, someone got
there before. Checkout nserver from
http://users.globalnet.co.uk/~syrinx/ if your interested in the Nokia
stuff.)

I feel that the concept could be taken a lot further, with various
filters and so on being constructed (given a framework in which to
construct them) similiar to that available with ethernet sniffers. This
could aid with the disassembly of unknown protocols over serial lines or
even for debugging serial connections. Maybe I'll write this code
someday, maybe not. Maybe someone else will and will send me a patch. :)


Command line options:

sersniff [-h] [-i DEVICE | -l PORT] [-o DEVICE | -c HOST:PORT] [-b BAUD] [-s]

-h
	Displays some command line option help.

-i IN_DEV
	Set the device to use for Port1, if you're using serial ports.
	Default of /dev/ttyS0

-l PORT
	Set the port to listen on, if you want Port1 to be a TCP socket.

-o OUT_DEV
	Set the device to use for Port2, if you're using serial ports.
	Default of /dev/ttyS1

-c HOST:PORT
	Specify the host and port to connect to if Port2 is to be a TCP
	socket.

-b BAUD
	Specify baud rate for serial connections. Defaults to 19200.

-s
	Make sersniff not copy data between the two ports - useful if a
	Y cable is being used for serial port sniffing for example.


TCP/serial things:

This program was originally written to cope with serial port data. I
have added simple support for a TCP connection both to aid with
development (it's a /lot/ easier for me to generate TCP streams than
serial streams) and also because I think a lot of the things that are
useful for monitoring a serial port data stream can also be applied to
TCP. Taking this further leads to thinking about UDP/raw ethernet - I'll
think about it once I get some filtering stuff in.

The TCP stuff does a simple listen on a port and then connects to the
host/port specified. I see no reason why it couldn't be used to allow
telneting to a serial port or connecting from a serial port to a TCP
port, but I haven't tested this.


Filtering:

This is a definite to do. For example, let's assume a regex based
scheme. We could implement the current filter as something like:

/\x0A/		<LF>
/\x0D/		<CR>
/\x1B/		<ESC>
/./		.

(Yeah, ok, I need to think about syntax. This doesn't cover the < 32 or
> 127 range)

But then say we learn a bit about our protocol? Let's assume VT100 for a
moment, then we might want:

/\x0A/		<LF>
/\x0D/		<CR>
/\x1B/		<ESC>
/\x1B[2J/	<Screen Clear>
/\x1B[0m/	<Attribute Reset>
/\0x7/		<BEL>
/./		.

Now that's more useful, isn't it? And if it came with filters for common
serial protocols, that might be useful too? Say a VT100 one, a PPP one,
a UUCP one, well, you get the idea hopefully.

Anyway, this is a major to do. Just needs me to get a round tuit and
think about syntax.


Development system:

sersniff was originally written under Linux on a 486dx2-66. It is
currently being worked on under FreeBSD on a Cyrix P233+.


Contacting the author:

I can be reached as noodles@earth.li or on Fidonet as Jonathan McDowell
@ 2:443/21

All constructive criticism about sersniff is welcome.


License:

sersniff is distributed under the GNU Public License, a copy of which
should have been provided with this archive as LICENSE.