Packing User Agent Header.

Hello All

i want to have few clarification regarding the kannel wap gateway. 
Listing out them:

1>#define PDU(name, docstring, fields, is_valid) struct name { 
fields } name;
what does this declaration means. we were not able to understand 
it.

2>In the Get request header portion we have added the User Agent 
Name and Value,
The User-agent:0x29
The Value can be either Nokia or Ericsson
Wap box is throwing an error: "Error parsing application-header" 
what might be the problem.
we want this user agent to be packet and send it with in the http 
header

regards
Nigar