What is UDH?
UDH - User Data Header, UDH is a binary structure which may be present at the start of a short message in the Short Message Service in GSM. It is used in case of port bassed or concatenated message.
Sample UDH (In Concatenation) :
05 00 03 0A 02 01
05 is the length of data field in the UDH
00 : Offset to indicate new part of UDH
03 : Concate Header
0A : Message Reference Number
02 : Total Count of message.
01 : Sequence Number.