Wireshark-users: Re: [Wireshark-users] filter rule to check specific message type

From: Guy Harris <guy@xxxxxxxxxxxx>
Date: Fri, 18 Apr 2008 18:59:24 -0700

On Apr 17, 2008, at 1:56 AM, Sudharsanan Ranganathan wrote:

How do I put a filter rule to check on specific message types during TCP transactions for file download? For ex. If I have msg_request, msg_accept, msg_reject. How to identify specific message types from a wireshark capture?

There's no easy way to do that in a capture filter.

In a display filter, however, *if* the protocol that has those message types makes the message type a filterable field, you can compare the value of that field against the value corresponding to a particular message type. You can either compare the numerical value of the filterable field, for example

	smb.cmd == 0x0

or, if the field has associated with it a list of names corresponding to the values, compare with the name as a string, for example

	smb.cmd == "Create Directory"

(both of which will compare the value of the "smb.cmd" field with 0, as 0 is the code for the SMB "Create Directory" request).