ESP8266 通过 MQTT 协议实现 LED 的远程控制

#include <ESP8266WiFi.h>

#include <PubSubClient.h>

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#define LED 2 // on-board LED D4

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// WiFi

const char *ssid = "xxx"; // Enter your WiFi name

const char *password = "xxxxxx";  // Enter WiFi password

​

// MQTT Broker

const char *mqtt_broker = "xx.xx.xx.xx"; // EMQX Server IP

const char *topic = "emqx/esp8266"; // MQTTX topic

const char *mqtt_username = "UART"; // EMQX Server User Name

const char *mqtt_password = "123456"; //EMQX Server User Password

const int mqtt_port = 1883;

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bool ledState = false;

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WiFiClient espClient;

PubSubClient client(espClient);

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void setup() {

    // Set software serial baud to 115200;

    Serial.begin(115200);

    delay(1000); // Delay for stability

​

    // 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");

​

    // Setting LED pin as output

    pinMode(LED, OUTPUT);

    digitalWrite(LED, LOW);  // Turn off the LED initially

​

    // Connecting to an MQTT broker

    client.setServer(mqtt_broker, mqtt_port);

    client.setCallback(callback);

    while (!client.connected()) {

        String client_id = "esp8266-client-";

        client_id += String(WiFi.macAddress());

        Serial.printf("The client %s connects to the public MQTT broker\n", client_id.c_str());

        if (client.connect(client_id.c_str(), mqtt_username, mqtt_password)) {

            Serial.println("Public EMQX MQTT broker connected");

        } else {

            Serial.print("Failed with state ");

            Serial.print(client.state());

            delay(2000);

        }

    }

​

    // Publish and subscribe

    client.publish(topic, "hello emqx");

    client.subscribe(topic);

}

​

void callback(char *topic, byte *payload, unsigned int length) {

    Serial.print("Message arrived in topic: ");

    Serial.println(topic);

    Serial.print("Message: ");

    String message;

    for (int i = 0; i < length; i++) {

        message += (char) payload;  // Convert *byte to string

    }

    Serial.print(message);

    if (message == "on" && !ledState) {

        digitalWrite(LED, LOW);  // Turn on the LED

        ledState = true;

    }

    if (message == "off" && ledState) {

        digitalWrite(LED, HIGH); // Turn off the LED

        ledState = false;

    }

    Serial.println();

    Serial.println("-----------------------");

}

​

void loop() {

    client.loop();

    delay(100); // Delay for a short period in each loop iteration

}