ESP32通过MQTT连接树莓派Node-RED失败，求解决方案

我正在开发基于ESP32与DHT11传感器的项目，目标是通过本地WiFi将ESP32采集的温湿度数据经Node-RED发送至树莓派，其中Node-RED作为MQTT服务器代理，但ESP32无法成功连接Node-RED。以下是ESP32上运行的Arduino代码及Node-RED相关配置截图，恳请各位提供解决建议。

ESP32 Arduino代码 #

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

// Wi-Fi credentials
const char* ssid = "hkst2023";
const char* password = "BEftsp2023#";

// MQTT broker configuration
const char* mqtt_server = "192.168.1.100";  // Replace with your Raspberry Pi's IP address
const int  mqtt_port = 1883;
const char *topic = "testing";
const char* mqtt_username = "mqtt123";          // MQTT username, if required
const char* mqtt_password = "00000000";          // MQTT password, if required

// DHT sensor configuration
#define DHTPIN 5              // DHT11 data pin (GPIO2 on ESP32)
#define DHTTYPE DHT11         // DHT sensor type

DHT dht(DHTPIN, DHTTYPE);

// Initialize MQTT client
WiFiClient espClient;
PubSubClient client(espClient);

void setup() {
  // Start DHT sensor
  dht.begin();

  // Connect to Wi-Fi
  Serial.begin(115200);
  Serial.println();
  Serial.print("Connecting to ");
  Serial.println(ssid);
  WiFi.begin(ssid, password);
  while (WiFi.status() != WL_CONNECTED) {
    delay(1000);
    Serial.print(".");
  }
  Serial.println();
  Serial.print("Connected to WiFi. IP address: ");
  Serial.println(WiFi.localIP());

  // Connect to MQTT broker
  client.setServer(mqtt_server, mqtt_port);
  // If your MQTT broker requires authentication:
  // client.setCredentials(mqtt_username, mqtt_password);
}

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

  // Read temperature and humidity from DHT sensor
  float humidity = dht.readHumidity();
  float temperature = dht.readTemperature();

  // Check if the reading was successful
  if (isnan(humidity) || isnan(temperature)) {
    Serial.println("Failed to read from DHT sensor!");
    delay(2000);
    return;
  }

  // Publish data to MQTT topics
  char tempStr[6];
  char humStr[6];
  dtostrf(temperature, 2, 2, tempStr);
  dtostrf(humidity, 2, 2, humStr);

  // MQTT topics for temperature and humidity
  const char* tempTopic = "esp32/temperature";
  const char* humTopic = "esp32/humidity";

  client.publish(tempTopic, tempStr);
  client.publish(humTopic, humStr);

  delay(5000);  // Delay for 5 seconds before the next reading
}

void reconnect() {
  // Loop until we're reconnected
  while (!client.connected()) {
    Serial.print("Attempting MQTT connection...");
    // Attempt to connect
    if (client.connect("ESP32Client")) {
      Serial.println("connected");
    } else { 
      Serial.print("failed, rc=");
      Serial.print(client.state());
      Serial.println(" try again in 5 seconds");
      delay(5000);
    }
  }
}

Node-RED配置截图 #

解决建议 #

• 启用MQTT认证：从截图看Node-RED的MQTT代理已配置用户名和密码，但代码中client.setCredentials被注释，必须取消注释这一行，否则连接会被拒绝。修改后代码片段：

  // Connect to MQTT broker
  client.setServer(mqtt_server, mqtt_port);
  // If your MQTT broker requires authentication:
  client.setCredentials(mqtt_username, mqtt_password);
  

• 确认IP地址正确性：核实树莓派的本地IP是否为192.168.1.100，可在树莓派终端执行hostname -I查看当前IP。
• 排查网络连通性：确保ESP32和树莓派在同一WiFi局域网，可通过ESP32串口输出确认WiFi连接成功，再在树莓派执行ping [ESP32的IP]测试连通性。
• 检查端口监听状态：在树莓派终端执行sudo lsof -i :1883，确认Node-RED的MQTT节点正在监听1883端口。
• 确保客户端ID唯一：client.connect("ESP32Client")中的客户端ID需在MQTT代理中唯一，避免与其他设备冲突导致连接失败。
• 查看Node-RED日志：通过树莓派终端node-red-start启动Node-RED查看日志，或在Node-RED界面右侧菜单栏点击"日志"，获取连接失败的具体报错信息。

内容的提问来源于stack exchange，提问作者yong jie