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# 连接 ESP32

本文主要介绍如何在 ESP32 项目中使用 PubSubClient ，实现客户端与 MQTT 服务器的连接、订阅、收发消息等功能。

作为 ESP8266 的升级版本，ESP32 (opens new window) 是物联网项目的理想选择。除了 Wi-Fi 模块，该模块还包含蓝牙 4.0 模块。双核 CPU 工作频率为 80 至 240 MHz，包含两个 Wi-Fi 和蓝牙模块以及各种输入和输出引脚。

本文将分别介绍通过 TCP 端口和 SSL/TLS 端口来连接 ESP32 客户端到 MQTT 服务器，对于使用 Serverless 部署的用户，请查看 SSL/TLS 端口连接示例。TCP 端口和 SSL/TLS 端口连接在连接设置部分略有不同，发布和订阅部分代码相同。

# 前置准备

在进行连接之前，您需要准备好 MQTT 服务器和客户端。

# 获得 MQTT 服务器

使用 EMQX 提供的 免费公共 MQTT 服务器 (opens new window)，该服务基于 EMQX 的 MQTT 物联网云平台 (opens new window) 创建。服务器接入信息如下：

  • Broker: broker.emqx.io
  • TCP Port: 1883
  • TLS/SSL Port: 8883

您也可以自己创建部署，在部署概览下可以查看到连接相关的信息，请确保部署状态为运行中。使用 TCP 端口或 TLS/SSL 端口 测试连接到 MQTT 服务器。

如果您是自己创建部署，请设置认证鉴权，在部署控制台认证鉴权 > 认证 中设置用户名和密码，用于连接验证。

# Arduino IDE

本文中使用 Arduino IDE (opens new window) 作为代码编辑和上传，Arduino 集成开发环境（或是 ArduinoIDE）包含了一个用于写代码的文本编辑器、一个消息区、一个文本控制台以及一个带有常用功能按钮和文本菜单的工具栏。软件连接 Arduino 和 Genuino 之后，能给所连接的控制板上传程序，还能与控制板相互通信。

# 安装依赖

在 Arduino IDE 中完成以下安装。

  1. 安装 ESP32 开发板。

    点击工具 -> 开发板 -> 开发板管理。搜索 ESP32，点击安装。

  2. 安装 PubSub client 库。

    点击项目 -> 加载库 -> 管理库...。搜索 PubSubClient，安装 PubSubClient by Nick O’Leary。

# 通过 TCP 端口连接

本章节介绍了如何在 Arduino IDE 中通过 TCP 端口连接 ESP32 和 MQTT 服务器。

  1. 导入 WiFi 和 PubSubClient 库。
#include <WiFi.h>
#include <PubSubClient.h>
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  1. 设置 Wi-Fi 名称和密码，以及 MQTT 服务器连接地址和端口。

示例代码将使用公共 MQTT 服务器来连接，公共 MQTT 服务器无需设置用户名和密码。如果您创建了部署，请在部署控制台找到相应的连接地址，请参考 Serverless 认证鉴权和专有版 / BYOC 认证鉴权设置用户名和密码。

// WiFi
const char *ssid = "mousse"; // Enter your WiFi name
const char *password = "qweqweqwe";  // Enter WiFi password

// MQTT Broker
const char *mqtt_broker = "broker.emqx.io";// broker address
const char *topic = "esp32/test"; // define topic 
const char *mqtt_username = "emqx"; // username for authentication
const char *mqtt_password = "public";// password for authentication
const int mqtt_port = 1883;// port of MQTT over TCP
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  1. 打开串行连接，以便于输出程序的结果并且连接到 Wi-Fi 网络。
// Set software serial baud to 115200;
Serial.begin(115200);
// connecting to a WiFi network
WiFi.begin(ssid, password);
while (WiFi.status() != WL_CONNECTED) {
    delay(500);
    Serial.println("Connecting to WiFi..");
}
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  1. 使用 PubSubClient 连接到公共 MQTT Broker。
client.setServer(mqtt_broker, mqtt_port);
client.setCallback(callback);
while (!client.connected()) {
    String client_id = "esp32-client-";
    client_id += String(WiFi.macAddress());
    Serial.printf("The client %s connects to the public mqtt broker\n", client_id.c_str());
    if (client.connect(client_id.c_str(), mqtt_username, mqtt_password)) {
        Serial.println("Public emqx mqtt broker connected");
    } else {
        Serial.print("failed with state ");
        Serial.print(client.state());
        delay(2000);
    }
}
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  1. MQTT 服务器连接成功后，ESP32 将向 MQTT 服务器发布消息和订阅 esp32/test 主题消息。
// publish and subscribe
client.publish(topic, "Hi EMQX I'm ESP32 ^^"); // publish message to the topic
client.subscribe(topic); // subscribe message from the topic
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  1. 设置回调函数将主题名称打印到串行端口并打印从 esp32/test 主题接收的消息。
void callback(char *topic, byte *payload, unsigned int length) {
    Serial.print("Message arrived in topic: ");
    Serial.println(topic);
    Serial.print("Message:");
    for (int i = 0; i < length; i++) {
        Serial.print((char) payload[i]);
    }
    Serial.println();
    Serial.println("-----------------------");
}
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完整代码示例如下:

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

// WiFi
const char *ssid = "mousse"; // Enter your WiFi name
const char *password = "qweqweqwe";  // Enter WiFi password

// MQTT Broker
const char *mqtt_broker = "broker.emqx.io";// broker address
const char *topic = "esp32/test"; // define topic 
const char *mqtt_username = "emqx"; // username for authentication
const char *mqtt_password = "public";// password for authentication
const int mqtt_port = 1883;// port of MQTT over TCP

WiFiClient espClient;
PubSubClient client(espClient);

void setup() {
 // Set software serial baud to 115200;
 Serial.begin(115200);
 // connecting to a WiFi network
 WiFi.begin(ssid, password);
 while (WiFi.status() != WL_CONNECTED) {
     delay(500);
     Serial.println("Connecting to WiFi..");
 }
 Serial.println("Connected to the WiFi network");
 //connecting to a mqtt broker
 client.setServer(mqtt_broker, mqtt_port);
 client.setCallback(callback);
 while (!client.connected()) {
     String client_id = "esp32-client-";
     client_id += String(WiFi.macAddress());
     Serial.printf("The client %s connects to the public mqtt broker\n", client_id.c_str());
     if (client.connect(client_id.c_str(), mqtt_username, mqtt_password)) {
         Serial.println("Public emqx mqtt broker connected");
     } else {
         Serial.print("failed with state ");
         Serial.print(client.state());
         delay(2000);
     }
 }
    // publish and subscribe
    client.publish(topic, "Hi EMQX I'm ESP32 ^^"); // publish message to the topic
    client.subscribe(topic); // subscribe message from the topic
}

void callback(char *topic, byte *payload, unsigned int length) {
 Serial.print("Message arrived in topic: ");
 Serial.println(topic);
 Serial.print("Message:");
 for (int i = 0; i < length; i++) {
     Serial.print((char) payload[i]);
 }
 Serial.println();
 Serial.println("-----------------------");
}

void loop() {
 client.loop();
}
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# 通过 TLS/SSL 端口连接

本章节介绍了如何在 Arduino IDE 中通过 TLS/SSL 端口连接 ESP32 和 MQTT 服务器。TCP 端口和 TLS/SSL 端口连接在连接设置部分略有不同，发布和订阅部分代码相同。

  1. 导入 WiFi 和 PubSubClient 库。
#include <WiFi.h>
#include <PubSubClient.h>
#include <WiFiClientSecure.h>
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  1. 设置 Wi-Fi 名称和密码，以及 MQTT 服务器连接地址和端口。

示例代码将使用公共 MQTT 服务器来连接，公共 MQTT 服务器无需设置用户名和密码。如果您创建了部署，请在部署控制台找到相应的连接地址，请参考 Serverless 认证鉴权和专有版 / BYOC 认证鉴权设置用户名和密码。。

// WiFi
const char *ssid = "mousse"; // Enter your WiFi name
const char *password = "qweqweqwe";  // Enter WiFi password

// MQTT Broker
const char *mqtt_broker = "broker.emqx.io";// broker address
const char *topic = "esp32/test"; // define topic 
const char *mqtt_username = "emqx"; // username for authentication
const char *mqtt_password = "public";// password for authentication
const int mqtt_port = 8883;// port of MQTT over TLS/SSL
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  1. 添加服务端证书。如果您在使用公共 MQTT Broker、Serverless 部署或基础版部署的 TLS/SSL 端口连接，在此下载 CA 证书 (opens new window)。 如您使用专业版 / BYOC 部署的 TLS/SSL 端口连接，请使用自己的服务端证书。
// load DigiCert Global Root CA ca_cert
const char * ca_cert = \
  "-----BEGIN CERTIFICATE-----\n"\
"MIIDrzCCApegAwIBAgIQCDvgVpBCRrGhdWrJWZHHSjANBgkqhkiG9w0BAQUFADBh\n"\
"MQswCQYDVQQGEwJVUzEVMBMGA1UEChMMRGlnaUNlcnQgSW5jMRkwFwYDVQQLExB3\n"\
"d3cuZGlnaWNlcnQuY29tMSAwHgYDVQQDExdEaWdpQ2VydCBHbG9iYWwgUm9vdCBD\n"\
"QTAeFw0wNjExMTAwMDAwMDBaFw0zMTExMTAwMDAwMDBaMGExCzAJBgNVBAYTAlVT\n"\
"MRUwEwYDVQQKEwxEaWdpQ2VydCBJbmMxGTAXBgNVBAsTEHd3dy5kaWdpY2VydC5j\n"\
"b20xIDAeBgNVBAMTF0RpZ2lDZXJ0IEdsb2JhbCBSb290IENBMIIBIjANBgkqhkiG\n"\
"9w0BAQEFAAOCAQ8AMIIBCgKCAQEA4jvhEXLeqKTTo1eqUKKPC3eQyaKl7hLOllsB\n"\
"CSDMAZOnTjC3U/dDxGkAV53ijSLdhwZAAIEJzs4bg7/fzTtxRuLWZscFs3YnFo97\n"\
"nh6Vfe63SKMI2tavegw5BmV/Sl0fvBf4q77uKNd0f3p4mVmFaG5cIzJLv07A6Fpt\n"\
"43C/dxC//AH2hdmoRBBYMql1GNXRor5H4idq9Joz+EkIYIvUX7Q6hL+hqkpMfT7P\n"\
"T19sdl6gSzeRntwi5m3OFBqOasv+zbMUZBfHWymeMr/y7vrTC0LUq7dBMtoM1O/4\n"\
"gdW7jVg/tRvoSSiicNoxBN33shbyTApOB6jtSj1etX+jkMOvJwIDAQABo2MwYTAO\n"\
"BgNVHQ8BAf8EBAMCAYYwDwYDVR0TAQH/BAUwAwEB/zAdBgNVHQ4EFgQUA95QNVbR\n"\
"TLtm8KPiGxvDl7I90VUwHwYDVR0jBBgwFoAUA95QNVbRTLtm8KPiGxvDl7I90VUw\n"\
"DQYJKoZIhvcNAQEFBQADggEBAMucN6pIExIK+t1EnE9SsPTfrgT1eXkIoyQY/Esr\n"\
"hMAtudXH/vTBH1jLuG2cenTnmCmrEbXjcKChzUyImZOMkXDiqw8cvpOp/2PV5Adg\n"\
"06O/nVsJ8dWO41P0jmP6P6fbtGbfYmbW0W5BjfIttep3Sp+dWOIrWcBAI+0tKIJF\n"\
"PnlUkiaY4IBIqDfv8NZ5YBberOgOzW6sRBc4L0na4UU+Krk2U886UAb3LujEV0ls\n"\
"YSEY1QSteDwsOoBrp+uvFRTp2InBuThs4pFsiv9kuXclVzDAGySj4dzp30d8tbQk\n"\
"CAUw7C29C79Fv1C5qfPrmAESrciIxpg0X40KPMbp1ZWVbd4="\
"-----END CERTIFICATE-----\n";

// init secure wifi client
WiFiClientSecure espClient;
// use wifi client to init mqtt client
PubSubClient client(espClient);
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  1. 打开串行连接，以便于输出程序的结果并且连接到 Wi-Fi 网络。
// Set software serial baud to 115200;
Serial.begin(115200);
// connecting to a WiFi network
WiFi.begin(ssid, password);
while (WiFi.status() != WL_CONNECTED) {
    delay(500);
    Serial.println("Connecting to WiFi..");
}
Serial.println("Connected to the WiFi network");
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  1. 设置证书并使用 PubSubClient 连接到公共 MQTT Broker。
// set root ca cert
espClient.setCACert(ca_cert);
// connecting to a mqtt broker
client.setServer(mqtt_broker, mqtt_port);
client.setCallback(callback);
while (!client.connected()) {
    String client_id = "esp32-client-";
    client_id += String(WiFi.macAddress());
    Serial.printf("The client %s connects to the public mqtt broker\n", client_id.c_str());
    if (client.connect(client_id.c_str(), mqtt_username, mqtt_password)) {
        Serial.println("Public emqx mqtt broker connected");
    } else {
        Serial.print("failed with state ");
        Serial.print(client.state());
        delay(2000);
    }
}
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  1. MQTT 服务器连接成功后，ESP32 将向 MQTT 服务器发布消息和订阅主题。
// publish and subscribe
client.publish(topic, "Hi EMQX I'm ESP32 ^^"); // publish message to the topic
client.subscribe(topic); // subscribe message from the topic
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  1. 设置回调函数将主题名称打印到串行端口并打印从 esp32/test 主题接收的消息。
void callback(char *topic, byte *payload, unsigned int length) {
    Serial.print("Message arrived in topic: ");
    Serial.println(topic);
    Serial.print("Message:");
    for (int i = 0; i < length; i++) {
        Serial.print((char) payload[i]);
    }
    Serial.println();
    Serial.println("-----------------------");
}
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完整代码示例如下：

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

// WiFi
const char *ssid = "mousse"; // Enter your WiFi name
const char *password = "qweqweqwe";  // Enter WiFi password

// MQTT Broker
const char *mqtt_broker = "broker.emqx.io";// broker address
const char *topic = "esp32/test"; // define topic 
const char *mqtt_username = "emqx"; // username for authentication
const char *mqtt_password = "public";// password for authentication
const int mqtt_port = 8883;// port of MQTT over TLS/SSL

// load DigiCert Global Root CA ca_cert
const char* ca_cert= \
"-----BEGIN CERTIFICATE-----\n" \
"MIIDrzCCApegAwIBAgIQCDvgVpBCRrGhdWrJWZHHSjANBgkqhkiG9w0BAQUFADBh\n" \
"MQswCQYDVQQGEwJVUzEVMBMGA1UEChMMRGlnaUNlcnQgSW5jMRkwFwYDVQQLExB3\n" \
"d3cuZGlnaWNlcnQuY29tMSAwHgYDVQQDExdEaWdpQ2VydCBHbG9iYWwgUm9vdCBD\n" \
"QTAeFw0wNjExMTAwMDAwMDBaFw0zMTExMTAwMDAwMDBaMGExCzAJBgNVBAYTAlVT\n" \
"MRUwEwYDVQQKEwxEaWdpQ2VydCBJbmMxGTAXBgNVBAsTEHd3dy5kaWdpY2VydC5j\n" \
"b20xIDAeBgNVBAMTF0RpZ2lDZXJ0IEdsb2JhbCBSb290IENBMIIBIjANBgkqhkiG\n" \
"9w0BAQEFAAOCAQ8AMIIBCgKCAQEA4jvhEXLeqKTTo1eqUKKPC3eQyaKl7hLOllsB\n" \
"CSDMAZOnTjC3U/dDxGkAV53ijSLdhwZAAIEJzs4bg7/fzTtxRuLWZscFs3YnFo97\n" \
"nh6Vfe63SKMI2tavegw5BmV/Sl0fvBf4q77uKNd0f3p4mVmFaG5cIzJLv07A6Fpt\n" \
"43C/dxC//AH2hdmoRBBYMql1GNXRor5H4idq9Joz+EkIYIvUX7Q6hL+hqkpMfT7P\n" \
"T19sdl6gSzeRntwi5m3OFBqOasv+zbMUZBfHWymeMr/y7vrTC0LUq7dBMtoM1O/4\n" \
"gdW7jVg/tRvoSSiicNoxBN33shbyTApOB6jtSj1etX+jkMOvJwIDAQABo2MwYTAO\n" \
"BgNVHQ8BAf8EBAMCAYYwDwYDVR0TAQH/BAUwAwEB/zAdBgNVHQ4EFgQUA95QNVbR\n" \
"TLtm8KPiGxvDl7I90VUwHwYDVR0jBBgwFoAUA95QNVbRTLtm8KPiGxvDl7I90VUw\n" \
"DQYJKoZIhvcNAQEFBQADggEBAMucN6pIExIK+t1EnE9SsPTfrgT1eXkIoyQY/Esr\n" \
"hMAtudXH/vTBH1jLuG2cenTnmCmrEbXjcKChzUyImZOMkXDiqw8cvpOp/2PV5Adg\n" \
"06O/nVsJ8dWO41P0jmP6P6fbtGbfYmbW0W5BjfIttep3Sp+dWOIrWcBAI+0tKIJF\n" \
"PnlUkiaY4IBIqDfv8NZ5YBberOgOzW6sRBc4L0na4UU+Krk2U886UAb3LujEV0ls\n" \
"YSEY1QSteDwsOoBrp+uvFRTp2InBuThs4pFsiv9kuXclVzDAGySj4dzp30d8tbQk\n" \
"CAUw7C29C79Fv1C5qfPrmAESrciIxpg0X40KPMbp1ZWVbd4=" \
"-----END CERTIFICATE-----\n";


// init secure wifi client
WiFiClientSecure espClient;
// use wifi client to init mqtt client
PubSubClient client(espClient); 


void setup() {
    // Set software serial baud to 115200;
    Serial.begin(115200);
    // connecting to a WiFi network
    WiFi.begin(ssid, password);
    while (WiFi.status() != WL_CONNECTED) {
        delay(500);
        Serial.println("Connecting to WiFi..");
    }
    Serial.println("Connected to the WiFi network");

    // set root ca cert
    espClient.setCACert(ca_cert);
    // connecting to a mqtt broker
    client.setServer(mqtt_broker, mqtt_port);
    client.setCallback(callback);
    while (!client.connected()) {
        String client_id = "esp32-client-";
        client_id += String(WiFi.macAddress());
        Serial.printf("The client %s connects to the public mqtt broker\n", client_id.c_str());
        if (client.connect(client_id.c_str(), mqtt_username, mqtt_password)) {
            Serial.println("Public emqx mqtt broker connected");
        } else {
            Serial.print("Failed to connect to MQTT broker, rc=");
            Serial.print(client.state());
            Serial.println("Retrying in 5 seconds.");
            delay(5000);
        }
    }
    // publish and subscribe
    client.publish(topic, "Hi EMQX I'm ESP32 ^^"); // publish message to the topic
    client.subscribe(topic); // subscribe message from the topic

}

void callback(char* topic, byte* payload, unsigned int length) {
    Serial.print("Message arrived in topic: ");
    Serial.println(topic);
    Serial.print("Message:");
    for (int i = 0; i < length; i++) {
        Serial.print((char) payload[i]);
    }
    Serial.println();
    Serial.println("-----------------------");
}

void loop() {
  if (!client.connected()) {
    reconnect();
  }
  client.loop();
}
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# 测试连接

在成功连接 MQTT 服务器后，您可以使用 Arduino IDE 和 MQTT X 测试连接。

  1. 请使用 Arduino IDE 将完整代码上传到 ESP32，并打开串口监视器，选择 115200 波特率查看 ESP32 连接情况。 esp32_connection
  2. 建立 MQTT X 客户端 与 MQTT 服务器的连接, 并向 ESP32 发送消息。 esp32_mqttx

# 更多内容

综上所述，我们实现了在 ESP32 项目中创建 MQTT 连接，模拟了使用客户端与 MQTT 服务器进行连接、订阅、收发消息的场景。可以在 这里 (opens new window) 下载到示例的源码，同时也可以在 GitHub (opens new window) 上找到更多其他语言的 Demo 示例。

← 使用 ESP32 + MicroPython 连接 →

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