02-ESP8266-MQTT Communication

Workflow

First understand the principle, then test further with MQTTx, and finally implement it on the ESP8266. Following this order means that if you hit a problem, you can track it down right away.

Check Whether the Firmware Works

AT+MQTTUSERCFG=0,1,"ESP8266Client","myname","password",0,0,""
If it doesn't throw an error, it works.
If it errors out, that means the firmware doesn't support MQTT — please flash the following firmware:
All the rest of this series is explained based on that firmware. If you really don't want to use the firmware below, please don't watch this video.

Flashing the Firmware

Use the firmware named 1471_esp8266-at_mqtt-1m
Hold the IO_O pin to ground and then power up to enter flashing mode, then flash the firmware as follows:

Communication Model

It uses the publish-subscribe model. In one sentence: as long as you subscribe to topic M, you'll receive whatever anyone else publishes to topic M.

Debugging Software MQTTX

The MQTT server has been switched — the new server's
IP is: 45.192.110.61
Server dashboard: http://45.192.110.61:18083
Username: test password: abc123456789

Using the AT Commands

Web Serial Debug Assistant Pro & Data Visualization
Pair it with the JSON file below for quick import:

Command	Purpose
AT+CWMODE=1	WiFi client mode
AT+CWJAP="aaa","aaaaaaaa"	Connect to WiFi
AT+MQTTUSERCFG=0,1,"ESP8266Client","myname","password",0,0,""	Set the MQTT parameters
AT+MQTTCONN=0,"45.192.110.61",1883,1	Connect to the MQTT server
AT+MQTTSUB=0,"test/topic",0	Subscribe to a topic
AT+MQTTPUB=0,"test/topic","Hello from ESP8266",0,0	Publish a message
AT+MQTTSUB?	View subscribed topics
AT+MQTTCLEAN=0	Close the server connection

Overall Workflow

1. Connect to WiFi
2. Set the client parameter info
3. Connect to the MQTT server
4. Subscribe to a topic, publish a message