esp8266.ino

#include <Arduino.h>

#include <ESP8266WiFi.h>
#include <Ticker.h>
#include <AsyncMqttClient.h>
#define WIFI_SSID "Error-404"
#define WIFI_PASSWORD "123452345"
#define LED_BUILTIN 2

#define MQTT_HOST IPAddress(192, 168, 1, 20) //MQTT BROKER IP ADDRESS

#define MQTT_PORT 1883
#define BROKER_USER "deepak"
#define BROKER_PASS "Letsfly1!"
AsyncMqttClient mqttClient;
Ticker mqttReconnectTimer;

WiFiEventHandler wifiConnectHandler;
WiFiEventHandler wifiDisconnectHandler;
Ticker wifiReconnectTimer;


unsigned long previousMillis = 0;   // Stores last time a message was published
const long interval = 10000;        // Interval at which to publish values

void connectToWifi() {
  Serial.println("Connecting to Wi-Fi...");
  WiFi.begin(WIFI_SSID, WIFI_PASSWORD);
}

void connectToMqtt() {
  Serial.println("Connecting to MQTT...");
  mqttClient.connect();
}

void onWifiConnect(const WiFiEventStationModeGotIP& event) {
  Serial.println("Connected to Wi-Fi.");
  connectToMqtt();
}

void onWifiDisconnect(const WiFiEventStationModeDisconnected& event) {
  Serial.println("Disconnected from Wi-Fi.");
  mqttReconnectTimer.detach(); // ensure we don't reconnect to MQTT while reconnecting to Wi-Fi
  wifiReconnectTimer.once(2, connectToWifi);
}

void onMqttConnect(bool sessionPresent) {
  Serial.println("Connected to MQTT.");
  Serial.print("Session present: ");
  Serial.println(sessionPresent);

  // Subscribe to topic "led" when it connects to the broker
  uint16_t packetIdSub = mqttClient.subscribe("led2", 0);
  Serial.print("Subscribing at QoS 2, packetId: ");
  Serial.println(packetIdSub);

  
}

void onMqttDisconnect(AsyncMqttClientDisconnectReason reason) {
  Serial.println("Disconnected from MQTT.");

  if (WiFi.isConnected()) {
    mqttReconnectTimer.once(2, connectToMqtt);
  }
}

void onMqttSubscribe(uint16_t packetId, uint8_t qos) {
  Serial.println("Subscribe acknowledged.");
  Serial.print("  packetId: ");
  Serial.println(packetId);
  Serial.print("  qos: ");
  Serial.println(qos);
}

void onMqttUnsubscribe(uint16_t packetId) {
  Serial.println("Unsubscribe acknowledged.");
  Serial.print("  packetId: ");
  Serial.println(packetId);
}

void onMqttMessage(char* topic, char* payload, AsyncMqttClientMessageProperties properties, size_t len, size_t index, size_t total) {
  // Do whatever you want when you receive a message

  // Save the message in a variable
  String receivedMessage;
  for (int i = 0; i < len; i++) {
    Serial.println((char)payload[i]);
    receivedMessage += (char)payload[i];
  }
  // Turn the LED on or off accordingly to the message content
  if (strcmp(topic, "led2") == 0) {
    if (receivedMessage == "true"){
      digitalWrite(LED_BUILTIN, HIGH);
    }
    if (receivedMessage == "false"){
      digitalWrite(LED_BUILTIN, LOW);
    }
  }
  
}



void setup() {
  Serial.begin(115200);
  Serial.println();
  Serial.println();
  pinMode (LED_BUILTIN, OUTPUT);
  digitalWrite(LED_BUILTIN, LOW);

  wifiConnectHandler = WiFi.onStationModeGotIP(onWifiConnect);
  wifiDisconnectHandler = WiFi.onStationModeDisconnected(onWifiDisconnect);

  mqttClient.onConnect(onMqttConnect);
  mqttClient.onDisconnect(onMqttDisconnect);
  mqttClient.onSubscribe(onMqttSubscribe);
  mqttClient.onUnsubscribe(onMqttUnsubscribe);
  mqttClient.onMessage(onMqttMessage);
  
  mqttClient.setServer(MQTT_HOST, MQTT_PORT);
  mqttClient.setCredentials(BROKER_USER, BROKER_PASS);


  connectToWifi();
}

void loop() {

  
}