Protocol MQTT

The MQTT protocol defines a lightweight and simple messaging protocol designed for limited devices and networks with low bandwidth, unreliable networks or high latency. The MQTT client uses publish and subscribe methods to communicate over a TCP connection with the MQTT message broker.

MQTT AT commands are implemented according to MQTT version 3.1.1.

Secure MQTT is not supported

# Enable URCs 
> AT+CEREG=2
< OK

# Read network registration status
> AT+CEREG?
< +CEREG: 2,2
< OK

# Read network registration status. Wait of +CEREG: 2,5...
> AT+CEREG?
< +CEREG: 2,5,"AB80","819965",9
< OK

# Check the module connected to the network
> AT+CGATT?
< +CGATT: 1
< OK

# Check to see if the PDP context has been activated.
> AT+CGACT?
< +CGACT: 1,1
< OK

# Read IP address from module
> AT+CGDCONT?
< +CGDCONT: 1,"IP","vgesace.nb.iot","10.254.46.241",0,0,0,0,0,0
< OK

# Set MQTT unique client ID. In the example IMEI from device
> AT+UMQTT=0,"350857128129037"
< +UMQTT: 0,1
< OK

# Set MQTT local TCP port number
> AT+UMQTT=1,1883
< +UMQTT: 1,1
< OK

# Set remote MQTT server's name
> AT+UMQTT=2,"broker.emqx.io"
< +UMQTT: 2,1
< OK

# Set remote MQTT server's IP address
> AT+UMQTT=3,"44.195.202.69",1883
< +UMQTT: 3,1
< OK

# Connect to the broker
> AT+UMQTTC=1
< +UMQTTC: 1,1
< OK

< +UUMQTTC: 1,0

""" Repeat the command "AT+UMQTTC=1" if the URC "+UUMQTTC: 1,0" does not arrive. """

# Subscribe to MQTT topic filter
> AT+UMQTTC=4,0,"/exelonix/test"
< +UMQTTC: 4,1
< OK

< +UUMQTTC: 4,1,0,"/exelonix/test"

# Publish MQTT message to topic name
> AT+UMQTTC=2,0,0,"/exelonix/test","MQTT message"
< +UMQTTC: 2,1
< OK

# Wait of asynchronous notification (URC) of the reception of an MQTT message
< +UUMQTTCM: 6,1

# Read MQTT messages received
> AT+UMQTTC=6
< +UMQTTC: 6,1
< OK

< +UUMQTTCM: 6,1

< Topic:/exelonix/test
< Msg:MQTT message

# Disconnect from the broker
> AT+UMQTTC=0
< +UMQTTC: 0,1
< OK