esp32 arduino mqtt的连接代码中mqttserver该怎么写，例子

如果你想在ESP32 Arduino中连接到MQTT服务器，以下是一个示例代码，你可以将其中的`mqttServer`变量替换为你的MQTT服务器地址：

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

// Replace the variables below with your network credentials and MQTT broker details
const char* ssid = "your_SSID";
const char* password = "your_PASSWORD";
const char* mqttServer = "your_MQTT_broker_server_address"; // 替换为你的MQTT服务器地址
const int mqttPort = 1883;
const char* mqttUser = "your_MQTT_username";
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("ESP32Client", mqttUser, mqttPassword )) {
      Serial.println("Connected to MQTT");
      client.subscribe("testTopic");
    } else {
      Serial.print("Failed with state ");
      Serial.print(client.state());
      delay(2000);
    }
  }
}

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

void callback(char* topic, byte* message, unsigned int length) {
  Serial.print("Message received on topic: ");
  Serial.print(topic);
  Serial.print(". Message: ");
  String messageTemp;
  for (int i = 0; i < length; i++) {
    messageTemp += (char)message[i];
  }
  Serial.println(messageTemp);
}

void reconnect() {
  while (!client.connected()) {
    Serial.println("Connecting to MQTT...");
    if (client.connect("ESP32Client", mqttUser, mqttPassword )) {
      Serial.println("Connected to MQTT");
      client.subscribe("testTopic");
    } else {
      Serial.print("Failed with state ");
      Serial.print(client.state());
      delay(2000);
    }
  }
}

在这个代码中，我们使用`mqttServer`变量来保存MQTT服务器地址，你只需要将它替换为你自己的MQTT服务器地址即可。