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Wireshark-users: Re: [Wireshark-users] Wireshark filter for cyclic messages

From: wsgd <wsgd@xxxxxxx>
Date: Tue, 08 Jun 2010 20:12:13 +0200
markus.proeller@xxxxxxx a �crit :

Hello list,

I have the following problem:
I'm capturing EtherNet/IP traffic with cyclic I/O messages. This means for instance, I start a conenction with a packet rate of 100ms.

I send a string, let's say 'test1' to the device and the device answers with 'test2'. I capture the following:

0 ms: -> test1
            <- test2
100ms: ->test1
                <- test2
200ms: ->test1
               <- test2
and so on... until I send a new command:
900ms: -> test3
               <- test4
1000ms: -> test3
                  <- test4

Is there a possibility to capture only the messages, where the message content is changing, like the following:
0 ms: ->test1
            <- test2
900ms: -> test3
               <- test4
capture : no possibility

display filter : if the dissector is specifically designed to handle the case
The dissector must specifiy a specific field "content_changed".
This field is set to false or true depending on a comparison with the previous packet.
Then you can use a display filter "myprotocol.content_changed == true".
http://wsgd.free.fr/ is able to do that.

I hope it got clear what I mean.

Thanks in advance

Markus
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