基于Arduino IDE 野火ESP8266模块 MQTT 的开发

一、库介绍

Arduino常用的MQTT库主要有PubSubClient。
PubSubClient库是一个广泛使用的MQTT客户端库，它基于MQTT 3.1.1版本，并且支持ESP8266和ESP32等Arduino兼容的硬件平台。PubSubClient库允许Arduino设备连接到MQTT服务器，发布和订阅MQTT主题，实现与其他设备或服务的通信。
在使用PubSubClient库时，需要将其包含在Arduino项目中，并配置MQTT服务器的地址、端口、客户端ID等参数。然后可以使用库提供的函数来建立MQTT连接、发布消息到特定的主题，以及订阅并处理接收到的消息。
除了PubSubClient库之外，还有其他一些MQTT库可供选择，但PubSubClient因其易用性和稳定性而广受欢迎。需要根据具体需求和项目环境选择适合的MQTT库。
安装完库，可查看官方的示例代码，查看方法如下：
在这里插入图片描述

官方示例代码如下：

/*Basic ESP8266 MQTT exampleThis sketch demonstrates the capabilities of the pubsub library in combinationwith the ESP8266 board/library.It connects to an MQTT server then:- publishes "hello world" to the topic "outTopic" every two seconds- subscribes to the topic "inTopic", printing out any messagesit receives. NB - it assumes the received payloads are strings not binary- If the first character of the topic "inTopic" is an 1, switch ON the ESP Led,else switch it offIt will reconnect to the server if the connection is lost using a blockingreconnect function. See the 'mqtt_reconnect_nonblocking' example for how toachieve the same result without blocking the main loop.To install the ESP8266 board, (using Arduino 1.6.4+):- Add the following 3rd party board manager under "File -> Preferences -> Additional Boards Manager URLs":http://arduino.esp8266.com/stable/package_esp8266com_index.json- Open the "Tools -> Board -> Board Manager" and click install for the ESP8266"- Select your ESP8266 in "Tools -> Board"
*/#include <ESP8266WiFi.h>
#include <PubSubClient.h>// Update these with values suitable for your network.const char* ssid = "........";
const char* password = "........";
const char* mqtt_server = "broker.mqtt-dashboard.com";WiFiClient espClient;
PubSubClient client(espClient);
unsigned long lastMsg = 0;
#define MSG_BUFFER_SIZE	(50)
char msg[MSG_BUFFER_SIZE];
int value = 0;void setup_wifi() {delay(10);// We start by connecting to a WiFi networkSerial.println();Serial.print("Connecting to ");Serial.println(ssid);WiFi.mode(WIFI_STA);WiFi.begin(ssid, password);while (WiFi.status() != WL_CONNECTED) {delay(500);Serial.print(".");}randomSeed(micros());Serial.println("");Serial.println("WiFi connected");Serial.println("IP address: ");Serial.println(WiFi.localIP());
}void callback(char* topic, byte* payload, unsigned int length) {Serial.print("Message arrived [");Serial.print(topic);Serial.print("] ");for (int i = 0; i < length; i++) {Serial.print((char)payload[i]);}Serial.println();// Switch on the LED if an 1 was received as first characterif ((char)payload[0] == '1') {digitalWrite(BUILTIN_LED, LOW);   // Turn the LED on (Note that LOW is the voltage level// but actually the LED is on; this is because// it is active low on the ESP-01)} else {digitalWrite(BUILTIN_LED, HIGH);  // Turn the LED off by making the voltage HIGH}}void reconnect() {// Loop until we're reconnectedwhile (!client.connected()) {Serial.print("Attempting MQTT connection...");// Create a random client IDString clientId = "ESP8266Client-";clientId += String(random(0xffff), HEX);// Attempt to connectif (client.connect(clientId.c_str())) {Serial.println("connected");// Once connected, publish an announcement...client.publish("outTopic", "hello world");// ... and resubscribeclient.subscribe("inTopic");} else {Serial.print("failed, rc=");Serial.print(client.state());Serial.println(" try again in 5 seconds");// Wait 5 seconds before retryingdelay(5000);}}
}void setup() {pinMode(BUILTIN_LED, OUTPUT);     // Initialize the BUILTIN_LED pin as an outputSerial.begin(115200);setup_wifi();client.setServer(mqtt_server, 1883);client.setCallback(callback);
}void loop() {if (!client.connected()) {reconnect();}client.loop();unsigned long now = millis();if (now - lastMsg > 2000) {lastMsg = now;++value;snprintf (msg, MSG_BUFFER_SIZE, "hello world #%ld", value);Serial.print("Publish message: ");Serial.println(msg);client.publish("outTopic", msg);}
}

二、代码设计

代码设计思路：
1.包含库：在Arduino项目中，包含必要的库文件，特别是MQTT库（如pubsubclient）。
2.WiFi设置：设置ESP8266连接到指定的WiFi网络所需的SSID和密码。
3.MQTT服务器设置：配置MQTT服务器的地址、端口以及任何必要的认证信息（如用户名和密码）。
4.回调函数：设置MQTT连接、发布和订阅的回调函数，以便处理与MQTT服务器的通信。
5.初始化和连接：在setup()函数中初始化MQTT客户端，并尝试连接到MQTT服务器。
6.消息处理：在loop()函数中处理MQTT消息，例如发布消息到特定的主题或响应订阅的主题消息。

测试代码如下：

#include <ESP8266WiFi.h>  
#include <PubSubClient.h>  // WiFi设置  
const char* ssid = "yourSSID";  
const char* password = "yourPASSWORD";  // MQTT服务器设置  
const char* mqtt_server = "yourMQTTServer";  
const int mqtt_port = 1883;  
const char* mqtt_client_id = "ESP8266Client";  
const char* mqtt_topic = "your/topic";  //
unsigned long lastMsg = 0;WiFiClient espClient;  
PubSubClient client(espClient);  void setup_wifi() {  delay(10);  // 连接到WiFi网络  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.print("IP address: ");  Serial.println(WiFi.localIP());  
}  void reconnect() {  // Loop until we're reconnected  while (!client.connected()) {  Serial.print("Attempting MQTT connection...");  // 连接到MQTT服务器  if (client.connect(mqtt_client_id)) {  Serial.println("connected");  // 一旦连接，订阅主题  client.subscribe(mqtt_topic);  } else {  delay(5000);  }  }  
}  void callback(char* topic, byte* payload, unsigned int length) {  // 处理接收到的消息  Serial.print("Message arrived [");  Serial.print(topic);  Serial.print("] ");  for (int i = 0; i < length; i++) {  Serial.print((char)payload[i]);  }  Serial.println();  
}  void setup() {  Serial.begin(115200);  setup_wifi();  client.setServer(mqtt_server, mqtt_port);  client.setCallback(callback);  
}  void loop() {  if (!client.connected()) {  reconnect();  }  client.loop();  // 每隔一段时间发布一条消息到MQTT主题  long now = millis();  if (now - lastMsg > 2000) {  lastMsg = now;  char msg[50];  snprintf(msg, 50, "hello world at %ld", now);  client.publish(mqtt_topic, msg);  }  
}

请确保上述代码中的yourSSID、yourPASSWORD、yourMQTTServer、your/topic替换为实际的SSID、密码、MQTT服务器地址和主题。
这个示例代码首先设置了WiFi连接，然后连接到MQTT服务器。一旦连接成功，它将订阅一个MQTT主题。在loop()函数中，它周期性地发布消息到该主题，并处理从该主题接收到的任何消息。
此外，MQTT服务器的地址、端口和凭据（如果需要的话）应根据实际的MQTT服务器配置进行调整。如MQTT服务器需要用户名和密码，PubSubClient库也提供了设置这些的方法。
上传成功后，打开串口监视器来查看ESP8266与MQTT服务器的通信日志。

三、测试结果

MQTT的参数配置如下：

// MQTT服务器设置  
const char* mqtt_server = "broker.mqtt-dashboard.com";  
const int mqtt_port = 1883;  
const char* mqtt_client_id = "ESP8266Client0326";  
const char* mqtt_topic = "test/topic";

esp8266模块运行串口打印如下：
在这里插入图片描述更换其它服务器进行测试，如下：