arduino euno如何向emqx发布消息

要使用 Arduino Uno 来发布消息到 EMQ X Broker，您需要使用 MQTT 协议。首先，您需要在 Arduino IDE 上安装 MQTT 库。然后，您可以使用以下代码将消息发布到指定的主题：

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

// Replace the following with your WiFi and MQTT details
const char* ssid = "your_SSID";
const char* password = "your_PASSWORD";
const char* mqttServer = "your_MQTT_SERVER";
const int mqttPort = 1883;
const char* mqttUser = "your_MQTT_USER";
const char* mqttPassword = "your_MQTT_PASSWORD";

WiFiClient espClient;
PubSubClient client(espClient);

void setup() {
  Serial.begin(115200);
  WiFi.begin(ssid, password);

  while (WiFi.status() != WL_CONNECTED) {
    delay(1000);
    Serial.println("Connecting to WiFi...");
  }

  Serial.println("Connected to WiFi");

  client.setServer(mqttServer, mqttPort);
  client.setCallback(callback);

  while (!client.connected()) {
    Serial.println("Connecting to MQTT...");

    if (client.connect("ArduinoClient", mqttUser, mqttPassword )) {
      Serial.println("connected");
    } else {
      Serial.print("failed with state ");
      Serial.print(client.state());
      delay(2000);
    }
  }
}

void loop() {
  client.loop();

  String message = "Hello, world!";
  client.publish("your_topic", message.c_str()); // replace "your_topic" with the topic you want to publish to
}

void callback(char* topic, byte* payload, unsigned int length) {
  // handle message received
}

在上面的代码中，`your_SSID` 和 `your_PASSWORD` 用于连接到 WiFi。`your_MQTT_SERVER` 是 EMQ X Broker 的地址，`mqttUser` 和 `mqttPassword` 用于认证。您需要将 `your_topic` 替换为您想要发布消息的实际主题。您可以将 `message` 替换为您要发布的消息。一旦上传到您的 Arduino Uno，它将开始发布消息。