一、前言

1、能够使用Arduino的软串口控制Esp8266接入网络，可以看看我的前两个博客。

2、了解MQTT协议，阿里云搭建MQTT服务器。

3、需要的库文件

WiFiEsp库是一个Arduino的封装好AT指令的WiFi操作库，可以使用Arduino的软串口操作

PubSubClient是一个用于Esp8266发布/订阅MQTT消息的库。

链接：https://pan.baidu.com/s/1mAaIbO3-SzVaN-jaaFwVbw 
提取码：ol2p

4、修改Esp8266串口波特率为9600

使用AT指令输入AT+UART_DEF=9600,8,1,0,0，如何使用AT指令请看Arduino Esp8266开发 （一）AT指令调试

5、参考的文章网址

二、Arduino代码

#include "DHT.h"
#include <WiFiEspClient.h>
#include <WiFiEsp.h>
#include <WiFiEspUdp.h>
#include <PubSubClient.h>
#include "SoftwareSerial.h"

#define WIFI_AP "xxxx"	//你家Wifi名称
#define WIFI_PASSWORD "****"	//密码

// DHT
#define DHTPIN 10		//DHT引脚
#define DHTTYPE DHT11
// 初始化DHT11传感器
DHT dht(DHTPIN, DHTTYPE);

char MqttServer[] = "1.11.111.0"; 	//MQTT服务器的IP地址（阿里云公网IP）
WiFiEspClient espClient;	// 初始化以太网客户端对象 -- WiFiEspClient.h
PubSubClient client(espClient);	// 初始化MQTT库PubSubClient.h的对象

SoftwareSerial mySerial(2, 3); // RX, TX，声明一个软串口

int status = WL_IDLE_STATUS;
unsigned long lastSend;

void setup() {

  Serial.begin(9600);
  dht.begin();
  
  InitWiFi();                                // 连接WiFi
  client.setServer( MqttServer, 1883 );      // 连接WiFi之后，连接MQTT服务器
  
  lastSend = 0;
}

void loop() {
  status = WiFi.status();
  if ( status != WL_CONNECTED) {
    while ( status != WL_CONNECTED) {
      Serial.print("[loop()]Attempting to connect to WPA SSID: ");
      Serial.println(WIFI_AP);
      // 连接WiFi热点
      status = WiFi.begin(WIFI_AP, WIFI_PASSWORD);
      delay(500);
    }
    Serial.println("[loop()]Connected to AP");
  }

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

  if ( millis() - lastSend > 1000 ) { // 用于定时1秒钟发送一次数据
    getAndSendTemperatureAndHumidityData(); // 获取温湿度数据发送到MQTT服务器上去
    lastSend = millis();
  }

  client.loop();
}

/*
 * 读取温湿度数据，然后发送到MQTT服务器上去
 */
void getAndSendTemperatureAndHumidityData()
{
  Serial.println("Collecting temperature data.");

  // 大概250ms读取一次
  float h = dht.readHumidity();
  float t = dht.readTemperature();

  // 查看是否读取温湿度失败的
  if (isnan(h) || isnan(t)) {
    Serial.println("Failed to read from DHT sensor!");
    return;
  }

  Serial.print("Humidity: ");
  Serial.print(h);
  Serial.print(" %\t");
  Serial.print("Temperature: ");
  Serial.print(t);
  Serial.print(" *C ");

  String temperature = String(t);
  String humidity = String(h);
  
  Serial.print( "Sending temperature and humidity : [" );
  Serial.print( temperature ); Serial.print( "," );
  Serial.print( humidity );
  Serial.print( "]   -> " );

  // 构建一个 JSON 格式的payload的字符串
  String payload = "{";
  payload += "\"temperature\":"; payload += temperature; payload += ",";
  payload += "\"humidity\":"; payload += humidity;
  payload += "}";
  char attributes[100];
  payload.toCharArray( attributes, 100 );
 
  client.publish( "DHT11", attributes );	//发布名字为“DHT11”的主题
  Serial.print("[publish]-->>");
  Serial.println( attributes );
}
/**
 *Wifi连接初始化
 */
void InitWiFi()
{
  // 初始化软串口，软串口连接ESP模块
  mySerial.begin(9600);
  // 初始化ESP模块
  WiFi.init(&mySerial);
  // 检测WiFi模块在不在，宏定义：WL_NO_SHIELD = 255,WL_IDLE_STATUS = 0,
  if (WiFi.status() == WL_NO_SHIELD) {
    Serial.println("WiFi shield not present");
    while (true);
  }

  Serial.println("[InitWiFi]Connecting to AP ...");
  // 尝试连接WiFi网络
  while ( status != WL_CONNECTED) {
    Serial.print("[InitWiFi]Attempting to connect to WPA SSID: ");
    Serial.println(WIFI_AP);
    status = WiFi.begin(WIFI_AP, WIFI_PASSWORD);
    delay(500);
  }
  Serial.println("[InitWiFi]Connected to AP");
}

/**
 * MQTT客户端断线重连函数
 */

void reconnect() {
  // 一直循环直到连接上MQTT服务器
  while (!client.connected()) {
    Serial.print("[reconnect]Connecting to MQTT Server ...");
    // 尝试连接connect是个重载函数 (clientId, username, password)
    if ( client.connect("mqttx_f4bb1f54", "zky", "135") ) {
    //设置客户端ID（自定义），用户名，密码
      Serial.println( "[DONE]" );
    } else {
      Serial.print( "[FAILED] [ mqtt connect error code = " );
      Serial.print( client.state() );
      Serial.println( " : retrying in 5 seconds]" );// Wait 5 seconds before retrying
      delay( 5000 );
    }
  }
}

三、效果
1、登录EMQ X Dashboard

2、连接客户端

3、订阅

4、发送和接收