mqtt smartconfig例程

MQTT SmartConfig 是一种将 MQTT 配置信息通过 Wi-Fi 配置的方法，可以使设备更加智能化。以下是一个 ESP32 上使用 MQTT SmartConfig 的例程：

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

// Replace with your network credentials
const char* ssid = "your_SSID";
const char* password = "your_PASSWORD";

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

WiFiClient espClient;
PubSubClient client(espClient);

void setup() {
  Serial.begin(115200);

  // Start WiFiSmartConfig
  WiFi.beginSmartConfig();

  Serial.println("Waiting for SmartConfig.");
  while (!WiFi.smartConfigDone()) {
    delay(500);
    Serial.print(".");
  }

  Serial.println("");
  Serial.println("SmartConfig received.");

  // Wait for WiFi to connect
  Serial.println("Connecting to WiFi");
  while (WiFi.status() != WL_CONNECTED) {
    delay(1000);
    Serial.print(".");
  }

  Serial.println("");
  Serial.println("WiFi connected");

  // Connect to MQTT broker
  client.setServer(mqtt_server, 1883);
  while (!client.connected()) {
    Serial.println("Connecting to MQTT broker...");
    if (client.connect("ESP32Client")) {
      Serial.println("Connected to MQTT broker");
    } else {
      Serial.print("Failed to connect to MQTT broker, rc=");
      Serial.print(client.state());
      Serial.println(" retrying in 5 seconds");
      delay(5000);
    }
  }

  // Subscribe to MQTT topic
  client.subscribe("test_topic");
}

void loop() {
  // Loop until MQTT client is connected
  while (!client.connected()) {
    Serial.println("Connecting to MQTT broker...");
    if (client.connect("ESP32Client")) {
      Serial.println("Connected to MQTT broker");
      client.subscribe("test_topic");
    } else {
      Serial.print("Failed to connect to MQTT broker, rc=");
      Serial.print(client.state());
      Serial.println(" retrying in 5 seconds");
      delay(5000);
    }
  }

  // Check for MQTT messages
  client.loop();

  // Publish MQTT message
  if (Serial.available()) {
    String msg = Serial.readString();
    client.publish("test_topic", msg.c_str());
  }
}

在这个例程中，我们使用了 `WiFiSmartConfig` 库来实现 MQTT SmartConfig。在 `setup()` 函数中，我们首先启动 WiFiSmartConfig，然后等待用户使用手机 APP 连接到设备并进行配置。一旦连接成功，我们就可以获取到 Wi-Fi 的 SSID 和密码，并使用它们来连接 Wi-Fi。之后，我们连接到 MQTT 代理并订阅一个测试主题。在 `loop()` 函数中，我们检查是否有 MQTT 消息到达并发布一个测试消息（来自串口）。在 `setup()` 和 `loop()` 函数中，我们都检查 MQTT 客户端是否已连接，如果没有，就会尝试重新连接。