pubsub.cpp

#include <WiFi.h>
#include <PubSubClient.h>

const char* ssid = "YOUR-SSID";
const char* password = "YOUR-PASSWORD";
const char* mqtt_server = "broker.mqtt-dashboard.com";

WiFiClient myClient;
PubSubClient client(myClient);
long lastMsg = 0;
char msg[50];
int value = 0;

void setup_wifi() {
  delay(10);
  Serial.println();
  Serial.print("Connecting to ");
  Serial.println(ssid);

  WiFi.begin(ssid, password);

  while (WiFi.status() != WL_CONNECTED) {
    delay(500);
    Serial.print(".");
  }

  Serial.println("");
  Serial.println("WiFi connected");
  Serial.println("IP address: ");
  Serial.println(WiFi.localIP());
}

void callback(char* topic, byte* payload, unsigned int length) {
  Serial.print("Message arrived [");
  Serial.print(topic);
  Serial.print("] ");
  for (int i = 0; i < length; i++) {
    Serial.print((char)payload[i]);
  }
  Serial.println();

  if ((char)payload[0] == '1') {
    Serial.println("Led Hidup");
    digitalWrite(LED_BUILTIN, LOW);
  } else {
    Serial.println("Led Mati");
    digitalWrite(LED_BUILTIN, HIGH);
  }
}

void reconnect() {
  while (!client.connected()) {
    Serial.print("Attempting MQTT connection...");
    if (client.connect("")) {
      Serial.println("connected");
      client.publish("espectro32/test/send", "hello world");
      client.subscribe("espectro32/test/receive");
    } else {
      Serial.println(" try again in 5 seconds");
      delay(5000);
    }
  }
}

void setup() {
  delay(10);
  pinMode(LED_BUILTIN, OUTPUT);
  Serial.begin(9600);
  setup_wifi();
  client.setServer(mqtt_server, 1883);
  client.setCallback(callback);
}

void loop() {

  if (!client.connected()) {
    reconnect();
  }
  client.loop();

  long now = millis();
  if (now - lastMsg > 7000) {
    lastMsg = now;
    ++value;
    snprintf (msg, 50, "hello world #%ld", value);
    Serial.print("Publish message: ");
    Serial.println(msg);
    client.publish("espectro32/test/send", msg);
  }
}