在ESP32使用mqtt publish與subscribe－No More Codes

要在ESP32上使用mqtt, 需先到 Sketch>Include Library>Manage 下載安裝 PubSubClient 程式庫, 以下為 ESP32 的程式

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

#define pinRelayLED 5
#define pinMqttStatusLED 12

// Update these with publishCounts suitable for your network.
const char* ssid = "........";
const char* password = "........";

const char* mqtt_server = "........";
const char* mqtt_id = "ESP32Client";
const char* mqtt_publish_topic = "esp32_msg";
const char* mqtt_subscribe_topic = "smarthome_msg";
const int mqtt_qos = 1; //0：at most once 1：at least once 2：exactly once）
const bool mqtt_retain = true;

WiFiClient espWiFiClient;
PubSubClient mqttClient(espWiFiClient);
long lastMsgMillis = 0;
char msg[50];
int publishCount = 0, reConnectCount=0;

void setup() {
pinMode(pinRelayLED, OUTPUT);     // Initialize the BUILTIN_LED pin as an output
digitalWrite(pinRelayLED, LOW);
pinMode(pinMqttStatusLED, OUTPUT);
for (int i=0; i<3; i++) {
    digitalWrite(pinMqttStatusLED, HIGH);
    delay(500);
    digitalWrite(pinMqttStatusLED, LOW);
    delay(500);
}

Serial.begin(115200);
setup_wifi();

mqttClient.setServer(mqtt_server, 1883);
mqttClient.setCallback(callback);

while (!mqttClient.connected()) { // Loop until we're connected
mqttConnect();
}
digitalWrite(pinMqttStatusLED, HIGH);
}

void setup_wifi() {
delay(10);
// We start by connecting to a WiFi network
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.print(" reConnectCount = ");
Serial.println(reConnectCount);

// Switch on the LED if an 1 was received as first character
if (payload[0] == '0') {
digitalWrite(pinRelayLED, LOW);
} else if (payload[0] == '1') {
digitalWrite(pinRelayLED, HIGH); // Turn the LED off by making the voltage HIGH
}
}

void mqttConnect() {
    Serial.print("Attempting MQTT connection...");
    // Attempt to connect
    boolean connectOK = mqttClient.connect(mqtt_id, mqtt_publish_topic, mqtt_qos, mqtt_retain); //, "esp32 connected");
    if (connectOK) { //deviceID
      Serial.println("mqtt broker connected");
      // Once connected, publish an announcement...
      mqttClient.publish(mqtt_publish_topic, "esp32 connected");
      // ... and resubscribe
      mqttClient.subscribe(mqtt_subscribe_topic, mqtt_qos);
      publishCount = 0; //reset count for test
    } else {
      Serial.print("failed, rc=");
      Serial.print(mqttClient.state());
      Serial.print(" reConnectCount = ");
      Serial.println(reConnectCount);
      //Serial.println(" try again in 5 seconds");
      // Wait 5 seconds before retrying
      delay(5000);
    }
}

void loop() {

if (!mqttClient.connected()) {
    mqttConnect();
    reConnectCount++;
    digitalWrite(pinMqttStatusLED, LOW);
} else {
    mqttClient.loop();
    long now = millis();
    if (now - lastMsgMillis > 2000) {
      lastMsgMillis = now;
      ++publishCount;
      snprintf (msg, 75, "hello world #%ld", publishCount);
      Serial.print("Publish message: ");
      Serial.println(msg);
      mqttClient.publish(mqtt_publish_topic, msg);
    }
}
}