How to encode binary SMS headers for multipart messages
From How2s
UDH= 0500030F0202 050003 = this part can be fixed 0F is a reference-ID for the whole concatenated SMS and can be changed if you like) 02 = The number of SMS:s that the concatenated SMS contains 02 = The number in the order of the SMS (01 for the first, 02 for the second, 03 for the third etc.) So this is number two in the concatenated SMS.
message header for message number 1 of 4:
BINHEAD=X0201000106050003010401
the encoded body:
BINBODY=5468616920466973682043616B65732028546F64204D616E20506C612920666F72203420706572732E205072657061726174696F6E2074696D653A2033306D696E0A0A496E6772656469656E74733A0A2D20466973682063616B653A3435306720776869746520666973682066696C6574730A2D33207473702072656420637572
