arduino mqtt示例

以下是一个简单的Arduino MQTT示例代码：

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

// WiFi连接参数
const char* ssid = "your_SSID";
const char* password = "your_PASSWORD";

// MQTT服务器参数
const char* mqtt_server = "your_MQTT_SERVER";
const int mqtt_port = 1883;
const char* mqtt_topic = "your_TOPIC";

// WiFi客户端和MQTT客户端
WiFiClient espClient;
PubSubClient client(espClient);

void setup() {
  // 初始化串口
  Serial.begin(9600);

  // 连接WiFi
  WiFi.begin(ssid, password);
  while (WiFi.status() != WL_CONNECTED) {
    delay(1000);
    Serial.println("Connecting to WiFi...");
  }
  Serial.println("Connected to WiFi");

  // 连接MQTT服务器
  client.setServer(mqtt_server, mqtt_port);
  while (!client.connected()) {
    if (client.connect("arduinoClient")) {
      Serial.println("Connected to MQTT server");
    } else {
      Serial.print("Failed to connect to MQTT server, rc=");
      Serial.print(client.state());
      Serial.println(" retrying...");
      delay(1000);
    }
  }

  // 订阅主题
  client.subscribe(mqtt_topic);
}

void loop() {
  // 检查WiFi连接
  if (WiFi.status() != WL_CONNECTED) {
    Serial.println("WiFi disconnected, reconnecting...");
    WiFi.begin(ssid, password);
    while (WiFi.status() != WL_CONNECTED) {
      delay(1000);
    }
    Serial.println("Connected to WiFi");
  }

  // 检查MQTT连接
  if (!client.connected()) {
    Serial.println("MQTT disconnected, reconnecting...");
    if (client.connect("arduinoClient")) {
      Serial.println("Connected to MQTT server");
      client.subscribe(mqtt_topic);
    } else {
      Serial.print("Failed to connect to MQTT server, rc=");
      Serial.print(client.state());
      Serial.println(" retrying...");
      delay(1000);
    }
  }

  // 处理MQTT消息
  client.loop();
}

// 订阅消息的回调函数
void callback(char* topic, byte* payload, unsigned int length) {
  Serial.print("Message arrived on topic: ");
  Serial.println(topic);
  Serial.print("Message: ");
  for (int i = 0; i < length; i++) {
    Serial.print((char)payload[i]);
  }
  Serial.println();
}

该代码连接到WiFi和MQTT服务器，并订阅一个主题。在循环中，它检查WiFi和MQTT连接，并在需要时重新连接。它还处理MQTT消息并将其打印到串口。您需要将代码中的“your_SSID”，“your_PASSWORD”，“your_MQTT_SERVER”和“your_TOPIC”替换为实际的值。