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Wireshark-dev: Re: [Wireshark-dev] Packet direction detection from dissector level

From: Jaap Keuter <[email protected]>
Date: Fri, 12 Feb 2010 07:49:11 +0100

There are a few ways to tackle this.
First is based on a known port number. Say the server port has a fixed value of 4444, you can check the pinfo to see if the sourceport is 4444. If so it's a server packet. If its destinationport is 4444 it is a client packet. If neither it's not your protocol.
If there's no fixed port, you can use a conversation. This allows you  
to track data trough time, see README.developer for more info.
Tabs vs. spaces. Preferred are spaces.  Next are opening tabs, so only  
at the start of the line. But first and foremost a consistent style is  

Send from my iPhone

On 12 feb 2010, at 02:31, Daniel Kozar <[email protected]> wrote:

I'm attempting to write a dissector of a protocol used by a Polish IM
system called Gadu-Gadu. It's my first "larger" C project, so please
don't expect results very soon, but I'll surely try to do my best. So
far, having read the dissector developer documentation
(README.developer) and the more general Developer's Guide, I've
started writing and instantly stumbled upon a problem.

The problem is - is there any way to know if the packet is being sent
by the client or the server? I've encountered it because every packet
in this protocol has a "type" field in its header, but some values
repeat themselves and mean something else when sent by a server and
something else when sent by a client. I'd be thankful for providing
any solutions on how to solve this.

Another question - is the indentation/tab-width/"tabs as spaces"
coding style strictly enforced? Or is it okay to use your own
(without, obviously, being crazy), preferably with comments from this
-> http://www.wireshark.org/tools/modelines.html <- included?

Thank you very much in advance,

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