Esp8266 接受订阅，控制输出

发布信息，控制ESP8266管脚电压，实现控制。

#include <ESP8266WiFi.h>

#include <PubSubClient.h>

#define LED D8

// WiFi

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

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

// MQTT Broker

const char *mqtt_broker = "192.168.3.200";

const char *topic = "led"; //订阅主题

const char *mqtt_username = "emqx";

const char *mqtt_password = " ";

const int mqtt_port = 1883;

WiFiClient espClient;

PubSubClient client(espClient);

void setup() {

    // Set software serial baud to 115200;

    Serial.begin(115200);

    pinMode(LED,OUTPUT);

    // 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()) {

        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 = message + (char) payload[i];  // convert *byte to string

    }

//    Serial.print(message);

    if (message == "on")  { digitalWrite(LED, HIGH); }  // LED on

    if (message == "off") { digitalWrite(LED, LOW); } // LED off

//    Serial.print("hello ");

    Serial.println();

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

}

void loop() {

    client.loop();

}

只要发送  on 或 off 给  订阅主题  led ，就能控制D8 脚 的高低电平，实现控制。