安装Eclipse Paho MQTT C++库
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安装依赖项：
sudo apt-get update sudo apt-get install libpaho-mqttpp-dev libpaho-mqtt-dev -
下载和编译Eclipse Paho MQTT C++库：
git clone https://github.com/eclipse/paho.mqtt.cpp.git cd paho.mqtt.cpp mkdir build cd build cmake .. make sudo make install
编写MQTT客户端程序
#include <iostream>
#include <string>
#include <chrono>
#include <thread>
#include "mqtt/async_client.h"// 定义MQTT服务器地址和客户端ID
const std::string SERVER_ADDRESS("tcp://mqtt.eclipse.org:1883");
const std::string CLIENT_ID("paho_cpp_async_publish_subscribe");const std::string TOPIC("test_topic");
const int QOS = 1;
const auto TIMEOUT = std::chrono::seconds(10);class callback : public virtual mqtt::callback,public virtual mqtt::iaction_listener
{// 消息到达时的回调函数void message_arrived(mqtt::const_message_ptr msg) override {std::cout << "Message arrived" << std::endl;std::cout << " topic: '" << msg->get_topic() << "'" << std::endl;std::cout << " payload: '" << msg->to_string() << "'" << std::endl;}// 连接丢失时的回调函数void connection_lost(const std::string& cause) override {std::cout << "\nConnection lost" << std::endl;if (!cause.empty())std::cout << "Cause: " << cause << std::endl;}// 订阅成功或失败时的回调函数void on_failure(const mqtt::token& tok) override {std::cout << "Subscription failed" << std::endl;}void on_success(const mqtt::token& tok) override {std::cout << "Subscription succeeded" << std::endl;}
};int main(int argc, char* argv[]) {// 创建MQTT异步客户端mqtt::async_client client(SERVER_ADDRESS, CLIENT_ID);// 设置回调函数callback cb;client.set_callback(cb);// 设置连接选项mqtt::connect_options connOpts;connOpts.set_clean_session(true);try {// 连接到MQTT服务器std::cout << "Connecting to the MQTT server..." << std::flush;mqtt::token_ptr conntok = client.connect(connOpts);conntok->wait();std::cout << "OK" << std::endl;// 订阅主题std::cout << "Subscribing to topic '" << TOPIC << "'..." << std::flush;client.subscribe(TOPIC, QOS, nullptr, cb);std::cout << "OK" << std::endl;// 发布消息std::string payload = "Hello, MQTT!";mqtt::message_ptr pubmsg = mqtt::make_message(TOPIC, payload);pubmsg->set_qos(QOS);client.publish(pubmsg)->wait_for(TIMEOUT);std::cout << "Message published" << std::endl;// 等待一段时间，以接收消息std::this_thread::sleep_for(std::chrono::seconds(10));// 断开连接std::cout << "Disconnecting from the MQTT server..." << std::flush;conntok = client.disconnect();conntok->wait();std::cout << "OK" << std::endl;}catch (const mqtt::exception& exc) {std::cerr << exc.what() << std::endl;return 1;}return 0;
}
编译和运行程序
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创建CMakeLists.txt：
cmake_minimum_required(VERSION 3.5) project(MQTTClient)set(CMAKE_CXX_STANDARD 11)find_package(PahoMqttCpp REQUIRED)add_executable(MQTTClient main.cpp) target_link_libraries(MQTTClient PahoMqttCpp::paho-mqttpp3)
