Digi XB3-C-A2-UT series User Manual page 31

Getting started with the XBee Smart Modem Development Kit
Description
byte 1 Length MSB (0)
byte 2 Length LSB (4)
byte 3 (M)
byte 4 (Q)
byte 5 (T)
byte 6 (T)
Protocol level
byte 7 Level (4)
Connect flags
CONNECT flags byte, see the table below for the bits.
byte 8
Keep alive
byte 9 Keep Alive MSB (0)
byte 10 Keep Alive LSB (60)
Client ID
byte 11 Length MSB (0)
byte 12 Length LSB (4)
byte 13 (D)
byte 14 (I)
byte 15 (G)
byte 16 (I)
The following table describes the fields in the packet:
Field name Description
Protocol Name The connect packet starts with the protocol name, which is MQTT. The length of
the protocol name (in bytes) is immediately before the name itself.
Protocol Level Refers to the version of MQTT in use, in this case a value of 4 indicates MQTT
version 3.1.1.
Connect Flags Indicate certain aspects of the packet. For simplicity, this example only sets the
Clean Session flag, which indicates to the client and broker to discard any previous
session and start a new one.
Keep Alive How often the client pings the broker to keep the connection alive; in this example
it is set to 60 seconds.
Digi XBee3 Cellular LTE-M Global Smart Modem User Guide
Get started with MQTT
Hex value
0x00
0x04
0x4D
0x51
0x54
0x54
0x04
0X02
0X00
0X3C
0x00
0x04
0x44
0x49
0x47
0x49
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