UDL with application port adressing in MC35

[jaydk]

udl change port

hi.

i am currently trying to make a PDU string which has application port adressing set in the UDH, but i am having a hard time figuring out the how to determine the UDL, for use in the siemens MC35 gsm modem..

anyway, here is my PDU String

07915892000000F051000B916407281553F80000AA0A060504C3500000E8329BFD4697D9EC37


and the output from PDUSPY

PDU LENGTH IS 38 BYTES
ADDRESS OF DELIVERING SMSC
NUMBER IS : +85290000000
TYPE OF NR. : International
NPI : ISDN/Telephone (E.164/163)

MESSAGE HEADER FLAGS
MESSAGE TYPE : SMS SUBMIT
REJECT DUPLICATES : NO
VALIDITY PERIOD : RELATIVE
REPLY PATH : NO
USER DATA HEADER : PRESENT
REQ. STATUS REPORT : NO
MSG REFERENCE NR. : 0 (0x00)

DESTINATION ADDRESS
NUMBER IS : +46708251358
TYPE OF NR. : International
NPI : ISDN/Telephone (E.164/163)

PROTOCOL IDENTIFIER (0x00)
MESSAGE ENTITIES : SME-to-SME
PROTOCOL USED : Implicit / SC-specific

DATA CODING SCHEME (0x00)
AUTO-DELETION : OFF
COMPRESSION : OFF
MESSAGE CLASS : NONE
ALPHABET USED : 7bit default

VALIDITY OF MESSAGE : 4 days

USER DATA PART OF SM
USER DATA LENGTH : 10 septets (should be 18)
UDH LENGTH : 6 octets
UDH : 05 04 C3 50 00 00
UDH ELEMENTS : 05 - Appl. port addressing 16bit
4 (0x04) Bytes Information Element
00000 : SOURCE port
is: allocated by IANA
50000 : DESTINATION port
is: unknown
--- DATA ----------------------
05 04 C3 50 00 00
USER DATA (TEXT) : hellohello

as mentioned, it is the USER DATA LENGTH i am having a hard time figuring out how to calculate in C#