Calculating a two byte header in message payload

James

I would start by collecting only 2 bytes. Convert those from hex to decimal and then collect that number of bytes before you release.

when CLIENT_ACCEPTED {
   TCP::collect 2
   set header_collected "false"
}

when CLIENT_DATA {

   if { not ($header_collected) } {
       Comment out one of the two binary scan lines below.
       use this form if lower order byte is last (big endian order)
      binary scan [TCP::payload] S message_length
       use this form if lower order byte is first (little endian order)
      binary scan [TCP::payload] s message_length

      if { $message_length > 0 } {
         set header_collected "true"
         log local0. "Collecting message with length $message_length"
         TCP::collect $message_length
       }
    } else {
       if we are here the actual message is collected.
      set actual_message_text [TCP::payload]
      TCP::release
    }
 }

Feel free to post what you have and we take a look.

Examples of binary scan:

% binary scan \x02\x00 s var1
1
% puts $var1
2
% binary scan \x00\x03 S var1
1
% puts $var1
3
%

http://tmml.sourceforge.net/doc/tcl/binary.html