电子说
ESP32 MQTT的库有很多,凌顺实验室(lingshunlab.com)这次主要使用AsyncMQTT_ESP32,以后有机会再更多的MQTT其他库的使用方法。
前提条件
树莓派部署本地的MQTT服务端,具体安装请查看以下连接:
https://lingshunlab.com/book/raspberry-pi/raspberry-pi-install-mosquitto-mqtt-server-and-test-mqtt
ESP32和树莓派在同一WIFI网络里面
效果实现
凌顺实验室(lingshunlab.com)在本示例展示了使用两个ESP32,分别实现发布MQTT的主题消息和订阅并输出MQTT的主题内容。当然,可能会问能不能一个ESP32同时又是发布者,又是订阅者?答案是可以的,因为作为客户端,都是对中间商做信息交换。
BOM
需要准备2个ESP32,
一个ESP32用于发布,
一个ESP32用于订阅。
库的安装
可以在Arduino IDE的库管理里搜索并安装:
点击菜单栏的「工具」---> 「库管理」,然后在搜索框中输入“AsyncMQTT_ESP32”,点击安装即可
下图在我本地已经安装好了:
又或者在Github中下载,并安装到Arduino的 "libraries"文件夹里
Github 地址:
https://github.com/khoih-prog/AsyncMQTT_ESP32
程序提点
1, 首先,需要加载AsyncMQTT_ESP32的库
#include
2,配置MQTT的服务器信息,可以是IP或者域名的方式
//#define MQTT_HOST IPAddress(192, 168, 100, 100) #define MQTT_HOST "broker.emqx.io" // Broker address #define MQTT_PORT 1883
3,设置主题,发布需要主题,订阅也需要主题
const char *Topic = "lingshunlab/ESP32"; // 主题
4,创建MQTT客户端的实例
// 创建MQTT客户端的实例,名为mqttClient AsyncMqttClient mqttClient;
5,认识mqttClient的可用的回调函数
当MQTT触发特定事件的时候,可以配置自定义的函数
mqttClient.onConnect(onMqttConnect); // 设置 当MQTT连接时的回调函数 mqttClient.onDisconnect(onMqttDisconnect); // 设置 当MQTT断开连接时的回调函数 mqttClient.onSubscribe(onMqttSubscribe); // 设置 当MQTT订阅主题时的回调函数 mqttClient.onUnsubscribe(onMqttUnsubscribe); // 设置 当MQTT取消订阅主题时的回调函数 mqttClient.onMessage(onMqttMessage); // 设置 当MQTT订阅主题时的回调函数 mqttClient.onPublish(onMqttPublish); // 设置 当取消MQTT订阅主题时的回调函数 mqttClient.setServer(MQTT_HOST, MQTT_PORT); // 设置 MQTT服务器信息
6, 连接MQTT服务器
mqttClient.setServer(MQTT_HOST, MQTT_PORT); //连接MQTT服务器
7,发布主题
通过以下代码,可以对配置好的主题发布消息
// 发布主题消息 uint16_t packetIdPub = mqttClient.publish(PubTopic, 2, true, "welcome to Lingshunlab.com"); Serial.print("Publisshing at QoS 2, packetId: "); Serial.println(packetIdPub); delay(2000);
8,订阅主题
通过以下代码,可以订阅配置好的主题
// 订阅MQTT主题,并QoS设置为2 uint16_t packetIdSub = mqttClient.subscribe(SubTopic, 2); Serial.print("Subscribing at QoS 2, packetId: "); Serial.println(packetIdSub);
9,当发生主题消息变化的时候的回调函数
mqttClient的回调函数有很多种,请仔细学习查看例子中其他的回调函数。在这里,特别说明一下onMessage的回调函数onMqttMessage(这个函数名称你可以自己定义,随喜),里面有不少参数,例如topic,payload等,其中payload即是消息的内容,可以通过输出显示。
void onMqttMessage(char* topic, char* payload, const AsyncMqttClientMessageProperties& properties, const size_t& len, const size_t& index, const size_t& total) { (void) payload; Serial.println("=====On MQTT Message====="); Serial.println("Publish received."); 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); Serial.print("payload: "); Serial.println(payload); // 输出消息内容 }
10,请查看AsyncMQTT_ESP32的官方例子
可以学习到FreeRTOS的多线程如何应用。
程序代码
发布主题de完整代码
#include// 配置 WIFI #define WIFI_SSID "***your wifi***" #define WIFI_PASSWORD "***your wifi password***" // 加载AsyncMQTT_ESP32库 #include // 配置MQTT服务器地址和端口 #define MQTT_HOST IPAddress(192,168,100,100) // Broker IP // #define MQTT_HOST "broker.emqx.io" // Broker address #define MQTT_PORT 1883 const char *PubTopic = "lingshunlab/ESP32"; // 发布消息的主题 AsyncMqttClient mqttClient; // 创建 MQTT客户端实例 void onMqttConnect(bool sessionPresent) // 编写对应的回调函数 { Serial.println("=====On MQTT Connect====="); Serial.print("Connected to MQTT broker: "); Serial.print(MQTT_HOST); Serial.print(", port: "); Serial.println(MQTT_PORT); Serial.print("PubTopic: "); Serial.println(PubTopic); } void onMqttDisconnect(AsyncMqttClientDisconnectReason reason) { (void) reason; Serial.println("Disconnected from MQTT."); } void onMqttSubscribe(const uint16_t& packetId, const uint8_t& qos) { Serial.println("Subscribe acknowledged."); Serial.print(" packetId: "); Serial.println(packetId); Serial.print(" qos: "); Serial.println(qos); } void onMqttUnsubscribe(const uint16_t& packetId) { Serial.println("Unsubscribe acknowledged."); Serial.print(" packetId: "); Serial.println(packetId); } void onMqttMessage(char* topic, char* payload, const AsyncMqttClientMessageProperties& properties, const size_t& len, const size_t& index, const size_t& total) { (void) payload; Serial.println("=====On MQTT Message====="); Serial.println("Publish received."); 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); Serial.print("payload: "); Serial.println(payload); // 输出消息内容 } void onMqttPublish(const uint16_t& packetId) { Serial.println("Publish acknowledged."); Serial.print(" packetId: "); Serial.println(packetId); } void setup() { Serial.begin(115200); while (!Serial && millis() < 5000); delay(500); // 连接WIFI WiFi.begin(WIFI_SSID, WIFI_PASSWORD); while (WiFi.waitForConnectResult() != WL_CONNECTED) { Serial.println("Connection Failed! Rebooting..."); delay(5000); ESP.restart(); // 重启esp32 } delay(500); mqttClient.onConnect(onMqttConnect); // 设置 当MQTT连接时的回调函数 mqttClient.onDisconnect(onMqttDisconnect); // 设置 当MQTT断开连接时的回调函数 mqttClient.onMessage(onMqttMessage); // 设置 当MQTT订阅主题时的回调函数 mqttClient.onPublish(onMqttPublish); // 设置 当取消MQTT订阅主题时的回调函数 mqttClient.setServer(MQTT_HOST, MQTT_PORT); // 设置 MQTT服务器信息 mqttClient.connect(); // 连接 MQTT delay(500); } void loop() { // 发布主题消息 uint16_t packetIdPub = mqttClient.publish(PubTopic, 2, true, "welcome to Lingshunlab.com"); Serial.print("Publisshing at QoS 2, packetId: "); Serial.println(packetIdPub); delay(2000); }
上传代码后,程序将会先连接WIFI,然后连接MQTT服务器,再之后每隔2秒发布一个对应主题的消息
订阅主题de完整代码
#include// 配置 WIFI #define WIFI_SSID "***your wifi***" #define WIFI_PASSWORD "***your wifi password***" // 加载 AsyncMQTT_ESP32 库 #include // 配置MQTT服务器地址和端口 #define MQTT_HOST IPAddress(192,168,1,55) // Broker IP // #define MQTT_HOST "broker.emqx.io" // Broker address #define MQTT_PORT 1883 const char *SubTopic = "lingshunlab/ESP32"; // 订阅的主题 AsyncMqttClient mqttClient; void onMqttConnect(bool sessionPresent) { Serial.println("=====On MQTT Connect====="); Serial.print("Connected to MQTT broker: "); Serial.print(MQTT_HOST); Serial.print(", port: "); Serial.println(MQTT_PORT); Serial.print("PubTopic: "); Serial.println(SubTopic); // 订阅MQTT主题,并QoS设置为2 uint16_t packetIdSub = mqttClient.subscribe(SubTopic, 2); Serial.print("Subscribing at QoS 2, packetId: "); Serial.println(packetIdSub); } void onMqttDisconnect(AsyncMqttClientDisconnectReason reason) { (void) reason; Serial.println("Disconnected from MQTT."); } void onMqttSubscribe(const uint16_t& packetId, const uint8_t& qos) { Serial.println("=====On MQTT Subscribe====="); Serial.println("Subscribe acknowledged."); Serial.print(" packetId: "); Serial.println(packetId); Serial.print(" qos: "); Serial.println(qos); } void onMqttUnsubscribe(const uint16_t& packetId) { Serial.println("Unsubscribe acknowledged."); Serial.print(" packetId: "); Serial.println(packetId); } void onMqttMessage(char* topic, char* payload, const AsyncMqttClientMessageProperties& properties, const size_t& len, const size_t& index, const size_t& total) { (void) payload; Serial.println("=====On MQTT Message====="); Serial.println("Publish received."); 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); Serial.print("payload: "); Serial.println(payload); } void setup() { Serial.begin(115200); while (!Serial && millis() < 5000); delay(500); // 连接WIFI WiFi.begin(WIFI_SSID, WIFI_PASSWORD); while (WiFi.waitForConnectResult() != WL_CONNECTED) { Serial.println("Connection Failed! Rebooting..."); delay(5000); ESP.restart(); } delay(500); mqttClient.onConnect(onMqttConnect); // 设置 当MQTT连接时的回调函数 mqttClient.onDisconnect(onMqttDisconnect); // 设置 当MQTT断开连接时的回调函数 mqttClient.onSubscribe(onMqttSubscribe); // 设置 当MQTT订阅主题时的回调函数 mqttClient.onUnsubscribe(onMqttUnsubscribe); // 设置 当取消MQTT订阅主题时的回调函数 mqttClient.onMessage(onMqttMessage); // 设置 当MQTT收到主题消息时的回调函数 mqttClient.setServer(MQTT_HOST, MQTT_PORT); // 设置 MQTT服务器信息 mqttClient.connect(); // 连接 MQTT delay(500); } void loop() { }
上传代码后,程序将会先连接WIFI,然后连接MQTT服务器,当连接MQTT时,则会订阅主题,之后每隔2秒就会收到主题发布的消息
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