cSMPP is an optional alternative communication protocol that can be used with Message Hub.

cSMPP PDU format

PDU component	Description	Length
Length	Overall length of PDU including the length component	2 bytes
Command bit sequence	SMPP command as bit sequence (see Command bit sequence)	Variable (bits)
Field bitmap	Bitmap indicating presence of SMPP PDU fields in fields segment	Variable (bits)
Fields	SMPP fields indicated in field bitmap. All other fields are assumed to be set to default values and not included in PDU.	Variable (bytes)

Command bit sequence and field bitmap are a continuous sequence of bits that is padded to bytes (e.g. 5 bits command bit sequence + 25 bits field bitmap = 30 bits which is then padded to 32 bits = 4 bytes).

Command bit sequence

SMPP command	Bit sequence
bind_transceiver	000000
bind_transceiver_resp	000001
bind_transmitter	000010
bind_transmitter_resp	000011
bind_receiver	000100
bind_receiver_resp	000101
submit_sm	100
submit_sm_resp	101
deliver_sm	110
deliver_sm_resp	111
data_sm	00110
data_sm_resp	00111
alert_notification	000110
enquire_link	0110
enquire_link_resp	0111
query_sm	010010
query_sm_resp	010011
cancel_sm	010100
cancel_sm_resp	010101
replace_sm	010110
replace_sm_resp	010111
unbind	0001110
unbind_resp	0001111
generic_nack	010000

cSMPP supports all SMPP v3.4 and v5 standard commands except outbound/_resp, submit_multi/_resp, broadcast_sm/_resp, query_broadcast/_resp and cancel_broadcast_sm/_resp.

Fields

Representation of fields in cSMPP PDUs is more closely aligned to type of field in favour of PDU size.

Field
validity_period	Absolute value only supported. Stored as 32-bit unsigned integer representing seconds since epoch..
schedule_delivery_time	Absolute value only supported. Stored as 32-bit unsigned integer representing seconds since epoch.