Example: Availability & Command Confirmation

// ============================================================================
// Virtuino Cloud — MQTT Availability & Command Confirmation (ESP32)
//
// Demonstrates, all wired up together:
//   - Bare MQTT topics (no account key, no /in//out/, no "device/" segment)
//   - Last Will (LWT) + birth message for instant online/offline detection
//   - Heartbeat, so a stuck-but-connected device is also detected
//   - Command confirmation (Tasmota-style echo) for a relay
//
// See /docs/mqtt_docs.html for full topic reference and connection
// settings, and /docs/mqtt_confirmed.html for the concepts this sketch
// implements.
//
// Library: PubSubClient by Nick O'Leary
// (Arduino IDE -> Sketch -> Include Library -> Manage Libraries -> "PubSubClient")
// ============================================================================

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

// ── Wi-Fi ────────────────────────────────────────────────────────────────
const char* ssid     = "YOUR_WIFI_SSID";
const char* wifiPass = "YOUR_WIFI_PASSWORD";

// ── Virtuino Cloud MQTT ─────────────────────────────────────────────────
// mqttUser is only ever used to LOG IN — it is never part of a topic.
const char* mqttHost = "cloud.virtuino.com";
const int   mqttPort = 1883;                    // use 8883 + WiFiClientSecure for TLS
const char* mqttUser = "vr-abcd1234";            // your Sub-account Key
const char* mqttPass = "YOUR_MQTT_PASSWORD";
String      clientId;                           // built in setup(): "device_" + chip ID

const int RELAY_PIN = 26;

// ── Topics ──────────────────────────────────────────────────────────────
// Bare topics only — no account key, no "device/" segment, no in/out.
// Must match the Device and Field names you created in Console -> Devices.
String deviceName = "esp32";
String topicRelay = deviceName + "/relay1";   // used for BOTH subscribe (command) and publish (confirmation)
String topicTemp  = deviceName + "/temperature";
String topicLWT   = deviceName + "/LWT";      // reserved field name — connection state, not a data field

const unsigned long HEARTBEAT_INTERVAL_MS = 60000;   // publish something at least this often
unsigned long lastHeartbeat = 0;
unsigned long lastTempPublish = 0;

WiFiClient   wifiClient;
PubSubClient mqtt(wifiClient);

// ── Incoming message handler ───────────────────────────────────────────
void onMessage(char* topic, byte* payload, unsigned int len) {
  String msg = "";
  for (unsigned int i = 0; i < len; i++) msg += (char)payload[i];
  Serial.println("[" + String(topic) + "] " + msg);

  if (String(topic) == topicRelay) {
    bool relayOn = (msg == "1");
    digitalWrite(RELAY_PIN, relayOn ? HIGH : LOW);

    // Confirmation: echo the value we just applied back on the SAME bare
    // topic. The broker keeps the "receive command" and "send confirmation"
    // directions on separate real topics automatically — no risk of the
    // device looping on its own message.
    mqtt.publish(topicRelay.c_str(), msg.c_str());
  }
}

void connectMQTT() {
  while (!mqtt.connected()) {
    Serial.print("Connecting to MQTT...");
    // Last Will registered at connect time: topic, QoS, retain, message.
    // Bare topic, no account key, no /in/ or /out/ — see mqtt_confirmed.html.
    if (mqtt.connect(clientId.c_str(), mqttUser, mqttPass,
                      topicLWT.c_str(), 1, true, "offline")) {
      Serial.println(" connected!");
      mqtt.subscribe(topicRelay.c_str());

      // Birth message — clears the retained "offline" from last time.
      mqtt.publish(topicLWT.c_str(), "online", true);

      // Publish current relay state once, so the dashboard starts in sync.
      mqtt.publish(topicRelay.c_str(), digitalRead(RELAY_PIN) ? "1" : "0");
    } else {
      Serial.print(" failed, rc="); Serial.println(mqtt.state());
      delay(5000);
    }
  }
}

void setup() {
  Serial.begin(115200);
  clientId = "device_" + String((uint32_t)ESP.getEfuseMac(), HEX);   // unique per chip — no account key needed
  pinMode(RELAY_PIN, OUTPUT);

  WiFi.begin(ssid, wifiPass);
  while (WiFi.status() != WL_CONNECTED) { delay(500); Serial.print("."); }
  Serial.println("\nWi-Fi connected: " + WiFi.localIP().toString());

  mqtt.setServer(mqttHost, mqttPort);
  mqtt.setCallback(onMessage);
  mqtt.setKeepAlive(30);   // broker declares the device dead after ~1.5x this interval
}

void loop() {
  if (!mqtt.connected()) connectMQTT();
  mqtt.loop();

  unsigned long now = millis();

  // Publish temperature every 10 seconds (replace with a real sensor reading).
  if (now - lastTempPublish > 10000) {
    lastTempPublish = now;
    float temp = random(200, 300) / 10.0;
    mqtt.publish(topicTemp.c_str(), String(temp, 2).c_str());
  }

  // Heartbeat: even if nothing else changes, publish something at least
  // this often, so "last seen" stays fresh for devices that would
  // otherwise stay quiet for long periods (Device Monitor still catches a
  // stuck-but-connected device — the LWT alone can't, since the TCP
  // connection is still alive).
  if (now - lastHeartbeat > HEARTBEAT_INTERVAL_MS) {
    lastHeartbeat = now;
    mqtt.publish(topicLWT.c_str(), "online", true);
  }
}