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This article introduces the knowledge of "how ESP8266 connects to the free EMQ X MQTT server". In the operation of actual cases, many people will encounter such a dilemma, so let the editor lead you to learn how to deal with these situations. I hope you can read it carefully and be able to achieve something!

MQTT is a lightweight and flexible Internet of things message exchange and data transfer protocol dedicated to achieving a balance between flexibility and hardware / network resources for IoT developers.

ESP8266 offers "integrated Wi-Fi SoC solutions" with low power consumption, compact design, and "stability" to meet the needs of customers. ESP8266 has a complete and systematic Wi-Fi network function, which can not only be used alone, but also can be carried on other hosts MCU as a slave.

In this project, we will implement ESP8266 to connect to a free public MQTT server operated and maintained by EMQ X Cloud, and use Arduino IDE to program ESP8266. EMQ X Cloud is a secure MQTT Internet of things cloud service platform launched by EMQ. It provides one-stop operation and maintenance escrow and unique isolated environment MQTT 5.0access service.

Required components of the Internet of things

ESP8266

Arduino IDE

MQTT X: an elegant cross-platform MQTT 5.0client tool

Free public MQTT server

Broker: broker.emqx.io

TCP Port: 1883

Websocket Port: 8083

ESP8266 Pub/Sub schematic diagram

ESP8266 code writing

First, we will import the ESP8266WiFi and PubSubClient libraries, which connect ESP8266 to the Wi-Fi network and PubSubClient libraries that enable ESP8266 to connect to MQTT servers to publish messages and subscribe to topics.

# include # include

Set the Wi-Fi name and password, as well as the MQTT server connection address and port

Const char * ssid = "name"; / / Enter your WiFi nameconst char * password = "pass"; / / Enter WiFi passwordconst char * mqtt_broker = "broker.emqx.io"; const int mqtt_port = 1883

Open a serial connection to output the results of the program and connect to the Wi-Fi network

/ / Set software serial baud to 115200 Connecting to WiFi.. Serial.begin (115200); / / connecting to a WiFi networkWiFi.begin (ssid, password); while (WiFi.status ()! = WL_CONNECTED) {delay (500); Serial.println ("Connecting to WiFi..");}

Set up the MQTT server, write a callback function, and print the connection information to the serial port monitor

Client.setServer (mqtt_broker, mqtt_port); client.setCallback (callback); while (! client.connected ()) {Serial.println ("Connecting to public emqx mqtt broker."); if (client.connect ("esp8266-client")) {Serial.println ("Public emqx mqtt broker connected");} else {Serial.print ("failed with state"); Serial.print (client.state ()); delay (2000) }} void callback (char * topic, byte * payload, unsigned int length) {Serial.print ("Message arrived in topic:"); Serial.println (topic); Serial.print ("Message:"); for (int I = 0; I < length; ionization +) {Serial.print ((char) payload [I]);} Serial.println () Serial.println ("-");}

After a successful connection to the MQTT server, ESP8266 will publish messages and subscribe topics to the MQTT server

/ / publish and subscribeclient.publish ("esp8266/test", "hello emqx"); client.subscribe ("esp8266/test")

Print the topic name to the serial port, and then print each byte of the message received

Void callback (char * topic, byte * payload, unsigned int length) {Serial.print ("Message arrived in topic:"); Serial.println (topic); Serial.print ("Message:"); for (int I = 0; I < length; iTunes +) {Serial.print ((char) payload [I]);} Serial.println (); Serial.println ("- -") }

Connection and testing of MQTT server

Please use Arduino IDE to upload the complete code to ESP8266 and turn on the serial monitor

Establish a connection between the MQTT X client and the MQTT server and send a message to the ESP8266

View the messages received by ESP8266 in the serial port monitor

Complete code # include # include const char * ssid = "name"; / / Enter your WiFi nameconst char * password = "pass"; / / Enter WiFi passwordconst char * mqtt_broker = "broker.emqx.io"; const int mqtt_port = 1883 female WiFiClient espClient;PubSubClient client (espClient); void setup () {/ / Set software serial baud to 115200; Serial.begin (115200); / / connecting to a WiFi network WiFi.begin (ssid, password) While (WiFi.status ()! = WL_CONNECTED) {delay (500); Serial.println ("Connecting to WiFi..");} Serial.println ("Connected to the WiFi network"); / / connecting to a mqtt broker client.setServer (mqtt_broker, mqtt_port); client.setCallback (callback); while (! client.connected ()) {Serial.println ("Connecting to public emqx mqtt broker.") If (client.connect ("esp8266-client")) {Serial.println ("Public emqx mqtt broker connected");} else {Serial.print ("failed with state"); Serial.print (client.state ()); delay (2000);} / / publish and subscribe client.publish ("esp8266/test", "hello emqx") Client.subscribe ("esp8266/test");} void callback (char * topic, byte * payload, unsigned int length) {Serial.print ("Message arrived in topic:"); Serial.println (topic); Serial.print ("Message:"); for (int I = 0; I < length; ionization +) {Serial.print ((char) payload [I]);} Serial.println () Serial.println ("- -");} void loop () {client.loop ();} "how ESP8266 connects to a free EMQ X MQTT server" ends here. Thank you for reading. If you want to know more about the industry, you can follow the website, the editor will output more high-quality practical articles for you!

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