On Sep 27, 2007, at 4:30 PM, Zongjun wrote:

> I could have 30 different kinds of messages and I just can't know  
> the fix length. However, using tcp_dissect_pdus you have to give the  
> fix length.

No.

Using tcp_dissect_pdus() you have to give:

        1) a fixed minimum length, which:

                includes all the data necessary to determine the message length;

                is no longer than the shortest message length;

        2) a routine that, given the minimum length worth of data, determines  
the message length.

What determines the message length in your protocol?

Is there a message length field in all messages, at the same offset  
from the beginning of the message in all messages?  If so, then the  
minimum length is the length of the message length field plus the  
length of the data preceding the message length field.

If not, is there a message type field in all messages, at the same  
offset from the beginning of the message in all messages, and can the  
length of the message be determined from the value of the message type  
field?  If so, then the minimum length is the length of the message  
type field plus the length of the data preceding the message length  
field.

If not, what else is used to determine the length of the message?
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