MQTT Basic (WOKWI ESP32 + MQTT Box )

 MQTT Basic (WOKWI  ESP32 + MQTT Box )

WOKWI程式

/*

 Basic ESP32 MQTT example

*/

#include <WiFi.h>

#include <PubSubClient.h>

// Update these with values suitable for your network.

const char* ssid = "Wokwi-GUEST";

const char* password = "";

//const char* mqtt_server = "broker.mqtt-dashboard.com";

const char* mqtt_server = "test.mosquitto.org";

WiFiClient espClient;

PubSubClient client(espClient);

#define LED 2

long lastMsg = 0;

char msg[50];

int value = 0;

//================================

void setup_wifi() {

  delay(10);

  // We start by connecting to a WiFi network

  Serial.println();

  Serial.print("Connecting to ");

  Serial.println(ssid);

  WiFi.begin(ssid, password);

  while (WiFi.status() != WL_CONNECTED) {

    delay(500);

    Serial.print(".");

  }

  randomSeed(micros());

  Serial.println("");

  Serial.println("WiFi connected");

  Serial.println("IP address: ");

  Serial.println(WiFi.localIP());

}

//============================================================

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

  printPayload(topic, message, length);  

}

void printPayload(char* topic, byte* message, unsigned int length) {

  // Printing Received Message

  Serial.print("Message received on topic: ");

  Serial.println(topic);

  String messageTemp;

  for(int i=0; i<length; i+=1) {

    messageTemp += (char)message[i];

  }

  if(String(topic) == "alex9ufo/esp32/led"){

      if(messageTemp=="ON"){

        Serial.println("Led ON");

        digitalWrite(LED,LOW);

      }  

      if(messageTemp=="OFF"){

        Serial.println("Led OFF");

        digitalWrite(LED,HIGH);

      }

  }

  Serial.println(messageTemp);

}

//============================================================

void reconnect() {

  // Loop until we're reconnected

  while (!client.connected()) {

    Serial.print("Attempting MQTT connection...");

    // Create a random client ID

    String clientId = "ESP32Client-";

    clientId += String(random(0xffff), HEX);

    // Attempt to connect

    if (client.connect(clientId.c_str())) {

      Serial.println("connected");

      // Once connected, publish an announcement...

      client.publish("alex9ufo/esp32/hello", "hello world");

      // ... and resubscribe

      client.subscribe("alex9ufo/esp32/led");

    } else {

      Serial.print("failed, rc=");

      Serial.print(client.state());

      Serial.println(" try again in 5 seconds");

      // Wait 5 seconds before retrying

      delay(5000);

    }

  }

}

//============================================================

void setup() {

  pinMode(LED, OUTPUT);     // Initialize the BUILTIN_LED pin as an output

  digitalWrite(LED,HIGH);

  Serial.begin(115200);

  setup_wifi();

  client.setServer(mqtt_server, 1883);

  client.setCallback(callback);

}

//============================================================

void loop() {

  if (!client.connected()) {

    reconnect();

  }

  client.loop();

  long now = millis();

  if (now - lastMsg > 8000) {

    lastMsg = now;

    ++value;

    snprintf (msg, 75, "hello world #%ld", value);

    Serial.print("Publish message: ");

    Serial.println(msg);

    client.publish("alex9ufo/esp32/hello", msg);

  }

}

//============================================================