Failed to Connect to MQTT broker using ESP8266

[ahmadaufash]

Please help me, i should finish this project as soon
I want to make project monitoring using ESP8266, MQTT, and Node-RED dashboard
but I have an issue that my serial monitors showing cannot connected to MQTT
"Failed to connect to MQTT broker, rc=-2"
I try to test my mqtt in CMD using Sub and Pub, i send some text and it works well. but in my project it's failed.
here is my code:

#include <Wire.h>
#include <Adafruit_MLX90614.h>
#include <Wire.h>
#include "MAX30100_PulseOximeter.h"
#include <ESP8266WiFi.h>
#include <PubSubClient.h>

// Replace with your Wi-Fi credentials
const char* ssid = "mywifi";
const char* password = "password";

// Replace with your MQTT broker IP address
const char* mqttServer = "127.0.0.1";
const int mqttPort = 1883;

// Replace with your MQTT topics
const char* mqttTopicTemp = "sensors/temperature";
const char* mqttTopicOxygen = "sensors/oxygen";

WiFiClient espClient;
PubSubClient client(espClient);

Adafruit_MLX90614 mlx = Adafruit_MLX90614();
PulseOximeter pox;

void onHeartRateBeatDetected()
{
  float hr = pox.getHeartRate();
  Serial.print("Heart rate:");
  Serial.println(hr);
}

void setup() {
  Serial.begin(115200);

  // Connect to Wi-Fi
  WiFi.begin(ssid, password);
  
  while (WiFi.status() != WL_CONNECTED) {
    delay(1000);
    Serial.println("Connecting to WiFi...");
  }
  
  Serial.println("Connected to WiFi");
  
  // Connect to MQTT broker
  client.setServer(mqttServer, mqttPort);
  
  while (!client.connected()) {
    if (client.connect("ESP8266Client")) {
      Serial.println("Connected to MQTT broker");
    }
    else {
      Serial.print("Failed to connect to MQTT broker, rc=");
      Serial.println(client.state());
      delay(2000);
    }
  }

  // Initialize sensors
  mlx.begin();
  pox.begin();

  // Set up a callback for pulse detection
  pox.setOnBeatDetectedCallback(onHeartRateBeatDetected);
}

void loop() {
  // Read temperature from MLX90614 sensor
  float temperature = mlx.readObjectTempC();
  
  // Convert temperature to string
  String tempPayload = String(temperature);
  
  // Publish temperature to MQTT topic
  client.publish(mqttTopicTemp, tempPayload.c_str());

  // Update pulse oximeter
  pox.update();

  // Read oxygen level from MAX30100 sensor
  if (pox.begin()) {
    float oxygen = pox.getSpO2();
  
    // Convert oxygen level to string
    String oxygenPayload = String(oxygen);
  
    // Publish oxygen level to MQTT topic
    client.publish(mqttTopicOxygen, oxygenPayload.c_str());
  }

  delay(1000);  // Adjust the delay based on your needs
}

[superbool]

Make sure your local PC "127.0.0.1" and the "mywifi" in the same wifi.
You can print you ESP8266's ip address and the PC ip address to check.