esp8266mqtt代码

下面是一个使用ESP8266连接MQTT服务器的示例代码，其中需要替换为您自己的WiFi和MQTT服务器信息：

#include <ESP8266WiFi.h>
#include <PubSubClient.h>

// Replace with your WiFi credentials
const char* ssid = "YOUR_SSID";
const char* password = "YOUR_PASSWORD";

// Replace with your MQTT broker address
const char* mqtt_server = "MQTT_SERVER_IP_ADDRESS";

WiFiClient espClient;
PubSubClient client(espClient);

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 reconnect() {
  // Loop until we're reconnected
  while (!client.connected()) {
    Serial.print("Attempting MQTT connection...");
    // Attempt to connect
    if (client.connect("ESP8266Client")) {
      Serial.println("connected");
      // Once connected, publish an announcement...
      client.publish("outTopic", "hello world");
      // ... and resubscribe
      client.subscribe("inTopic");
    } else {
      Serial.print("failed, rc=");
      Serial.print(client.state());
      Serial.println(" try again in 5 seconds");
      // Wait 5 seconds before retrying
      delay(5000);
    }
  }
}

void setup() {
  Serial.begin(115200);
  setup_wifi();
  client.setServer(mqtt_server, 1883);
}

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

上述代码中，我们首先连接到WiFi网络，然后连接到MQTT服务器。如果连接失败，则将在5秒后重试连接。一旦连接成功，我们将发布“ hello world”消息并订阅“ inTopic”主题。

您可以使用`client.publish()`和`client.subscribe()`函数来发布和订阅其他主题。在`loop()`函数中，我们检查是否连接到MQTT服务器，并使用`client.loop()`函数来处理传入和传出消息。