#include <WiFi.h>
#include <PubSubClient.h>
// ---------------- WIFI ----------------
const char* ssid = "Wokwi-GUEST"; // Change if using real WiFi
const char* password = "";
// ---------------- MQTT ----------------
const char* mqttServer = "broker.hivemq.com";
const int mqttPort = 1883;
const char* subscribeTopic = "esp32/wokwi/MQTT";
// Clients
WiFiClient espClient;
PubSubClient client(espClient);
// --------------- CALLBACK ---------------
void callback(char* topic, byte* payload, unsigned int length) {
Serial.println("\n----- Message Received -----");
Serial.print("Topic: ");
Serial.println(topic);
Serial.print("Message: ");
for (int i = 0; i < length; i++) {
Serial.print((char)payload[i]);
}
Serial.println("\n----------------------------");
}
// --------------- WIFI CONNECT ---------------
void connectWiFi() {
Serial.print("Connecting to WiFi");
WiFi.begin(ssid, password);
while (WiFi.status() != WL_CONNECTED) {
delay(500);
Serial.print(".");
}
Serial.println("\nWiFi Connected!");
Serial.print("IP Address: ");
Serial.println(WiFi.localIP());
}
// --------------- MQTT RECONNECT ---------------
void reconnectMQTT() {
while (!client.connected()) {
Serial.print("Connecting to MQTT...");
// Create unique client ID
String clientId = "ESP32Client-";
clientId += String(random(1000, 9999));
if (client.connect(clientId.c_str())) {
Serial.println("Connected!");
client.subscribe(subscribeTopic);
Serial.print("Subscribed to: ");
Serial.println(subscribeTopic);
} else {
Serial.print("failed, rc=");
Serial.print(client.state());
Serial.println(" retrying in 5 seconds...");
delay(5000);
}
}
}
// --------------- SETUP ---------------
void setup() {
Serial.begin(115200);
delay(1000);
randomSeed(micros()); // For unique client ID
connectWiFi();
client.setServer(mqttServer, mqttPort);
client.setCallback(callback);
client.setBufferSize(512);
}
// --------------- LOOP ---------------
void loop() {
if (!client.connected()) {
reconnectMQTT();
}
client.loop();
}