MQTT②创建客户端发送温度数据
此篇教程的内容是跟随【零知ESP32教程】MQTT①服务器搭建
我们在MQTT①中已经搭建好了服务器，接下来就可以使用这个服务器发送和接收消息了。 需要注意的是，要记住服务器的IP地址，才能进行连接。
下面是整个通信流程的示意图：
ESP32＃1 已订阅esp32/led主题，并且在主题esp32/temperature下发布温度读数。
按下ESP32＃2 按钮时，它会在esp32/led主题下发布消息，以控制连接到ESP32＃1的LED。
ESP32＃2 已订阅esp32/temperature主题，以接收温度读数并将其显示在LCD上。
一、软件和硬件
sht3x的引脚说明：
EPS32#1 连线：
打开零知开源工具安装MQTT所依赖的库：
AsyncMqttClient.zip(点击下载)
AsyncTCP.zip(点击下载)
安装完成后如图：
SHT3X驱动文件，解压后放在项目目录下即可。
注意：在导入代码之后，要在第10，11行替换自己的WiFi名称和密码。 在第15行替换自己的MQTT服务器IP地址。
#include <WiFi.h>
extern "C" {
#include "freertos/FreeRTOS.h"
#include "freertos/timers.h"
}
#include <AsyncMqttClient.h>
#include "HTU3X.h"
// Change the credentials below, so your ESP32 connects to your router
#define WIFI_SSID "REPLACE_WITH_YOUR_SSID"
#define WIFI_PASSWORD "REPLACE_WITH_YOUR_PASSWORD"
// Change the MQTT_HOST variable to your IP address,
// so it connects to your Mosquitto MQTT broker
#define MQTT_HOST IPAddress(192, 168, X, XXX)
#define MQTT_PORT 1883
// Create objects to handle MQTT client
AsyncMqttClient mqttClient;
TimerHandle_t mqttReconnectTimer;
TimerHandle_t wifiReconnectTimer;
HTU3X myHumidity;//SDA = 21,SCL = 22
String temperatureString = ""; // Variable to hold the temperature reading
unsigned long previousMillis = 0; // Stores last time temperature was published
const long interval = 5000; // interval at which to publish sensor readings
const int ledPin = 25; // GPIO where the LED is connected to
int ledState = LOW; // the current state of the output pin
void connectToWifi() {
Serial.println("Connecting to Wi-Fi...");
WiFi.begin(WIFI_SSID, WIFI_PASSWORD);
}
void connectToMqtt() {
Serial.println("Connecting to MQTT...");
mqttClient.connect();
}
void WiFiEvent(WiFiEvent_t event) {
Serial.printf("[WiFi-event] event: %d\n", event);
switch(event) {
case SYSTEM_EVENT_STA_GOT_IP:
Serial.println("WiFi connected");
Serial.println("IP address: ");
Serial.println(WiFi.localIP());
connectToMqtt();
break;
case SYSTEM_EVENT_STA_DISCONNECTED:
Serial.println("WiFi lost connection");
xTimerStop(mqttReconnectTimer, 0); // ensure we don't reconnect to MQTT while reconnecting to Wi-Fi
xTimerStart(wifiReconnectTimer, 0);
break;
}
}
// Add more topics that want your ESP32 to be subscribed to
void onMqttConnect(bool sessionPresent) {
Serial.println("Connected to MQTT.");
Serial.print("Session present: ");
Serial.println(sessionPresent);
// ESP32 subscribed to esp32/led topic
uint16_t packetIdSub = mqttClient.subscribe("esp32/led", 0);
Serial.print("Subscribing at QoS 0, packetId: ");
Serial.println(packetIdSub);
}
void onMqttDisconnect(AsyncMqttClientDisconnectReason reason) {
Serial.println("Disconnected from MQTT.");
if (WiFi.isConnected()) {
xTimerStart(mqttReconnectTimer, 0);
}
}
void onMqttSubscribe(uint16_t packetId, uint8_t qos) {
Serial.println("Subscribe acknowledged.");
Serial.print(" packetId: ");
Serial.println(packetId);
Serial.print(" qos: ");
Serial.println(qos);
}
void onMqttUnsubscribe(uint16_t packetId) {
Serial.println("Unsubscribe acknowledged.");
Serial.print(" packetId: ");
Serial.println(packetId);
}
void onMqttPublish(uint16_t packetId) {
Serial.println("Publish acknowledged.");
Serial.print(" packetId: ");
Serial.println(packetId);
}
// You can modify this function to handle what happens when you receive a certain message in a specific topic
void onMqttMessage(char* topic, char* payload, AsyncMqttClientMessageProperties properties, size_t len, size_t index, size_t total) {
String messageTemp;
for (int i = 0; i < len; i++) {
//Serial.print((char)payload[i]);
messageTemp += (char)payload[i];
}
// Check if the MQTT message was received on topic esp32/led
if (strcmp(topic, "esp32/led") == 0) {
// If the LED is off turn it on (and vice-versa)
if (ledState == LOW) {
ledState = HIGH;
} else {
ledState = LOW;
}
// Set the LED with the ledState of the variable
digitalWrite(ledPin, ledState);
}
Serial.println("Publish received.");
Serial.print(" message: ");
Serial.println(messageTemp);
Serial.print(" topic: ");
Serial.println(topic);
Serial.print(" qos: ");
Serial.println(properties.qos);
Serial.print(" dup: ");
Serial.println(properties.dup);
Serial.print(" retain: ");
Serial.println(properties.retain);
Serial.print(" len: ");
Serial.println(len);
Serial.print(" index: ");
Serial.println(index);
Serial.print(" total: ");
Serial.println(total);
}
void setup() {
// Define LED as an OUTPUT and set it LOW
pinMode(ledPin, OUTPUT);
digitalWrite(ledPin, LOW);
Serial.begin(115200);
mqttReconnectTimer = xTimerCreate("mqttTimer", pdMS_TO_TICKS(2000), pdFALSE, (void*)0, reinterpret_cast<TimerCallbackFunction_t>(connectToMqtt));
wifiReconnectTimer = xTimerCreate("wifiTimer", pdMS_TO_TICKS(2000), pdFALSE, (void*)0, reinterpret_cast<TimerCallbackFunction_t>(connectToWifi));
WiFi.onEvent(WiFiEvent);
myHumidity.begin();
mqttClient.onConnect(onMqttConnect);
mqttClient.onDisconnect(onMqttDisconnect);
mqttClient.onSubscribe(onMqttSubscribe);
mqttClient.onUnsubscribe(onMqttUnsubscribe);
mqttClient.onMessage(onMqttMessage);
mqttClient.onPublish(onMqttPublish);
mqttClient.setServer(MQTT_HOST, MQTT_PORT);
connectToWifi();
}
void loop() {
unsigned long currentMillis = millis();
// Every X number of seconds (interval = 5 seconds)
// it publishes a new MQTT message on topic esp32/temperature
if (currentMillis - previousMillis >= interval) {
// Save the last time a new reading was published
previousMillis = currentMillis;
// New temperature readings
float humd, temp;
myHumidity.readTempAndHumi(&temp, &humd);
temperatureString = " " + String(temp) + "C " + String(32 + temp * 1.8) +
"F";
Serial.println(temperatureString);
// Publish an MQTT message on topic esp32/temperature with Celsius and Fahrenheit temperature readings
uint16_t packetIdPub2 = mqttClient.publish("esp32/temperature", 2, true, temperatureString.c_str());
Serial.print("Publishing on topic esp32/temperature at QoS 2, packetId: ");
Serial.println(packetIdPub2);
}
}
验证程序后并上传到ESP32，打开调试窗口，可以看到已经成功连入MQTT服务器，并且发送主题为 esp32/temperature 的消息：
