User Data Header(UDH) in a SMS

Hello all
I'm a little bit confused about using the udh-parameter in a HTTP-request.
I need an optional Header with a Port-Number in it. So i tried it like this:
http://localhost:13013/cgi-bin/sendsms?username=tester&password=foobar&to=+41xxxxxx&text=eine+SMS&udh=1000
But there is something wrong, otherwise I wouldn't get an errormessage.:)
Status: 400 Answer: <UDH field misformed, rejected>
Any idea what the reason could be? Do I need any option in the kannel.conf for
using an optional udh?

Best regards
Florian Schlums

 _  _ ___ ___  Florian Schlums;
| || / __| _ \ HSR Hochschule Rapperswil; Oberseestrasse 10;
| __ \__ \   / CH-8640 Rapperswil; Tel: +41 55 222 41 11;
|_||_|___/_|_\ EMAIL: fschlums@xxxxxx; WWW: www.hsr.ch
               My LinuxPage: http://mypage.bluewin.ch/schlums