C++ mqtt 实现客户端和服务端

在C++中，你可以使用Paho MQTT C++客户端库来实现MQTT客户端和服务端。以下是一个简单的示例，演示如何使用Paho MQTT C++库实现MQTT客户端和服务端：

客户端：

#include "mqtt/async_client.h"

const std::string ADDRESS { "tcp://localhost:1883" };
const std::string CLIENT_ID { "async_publish" };

int main(int argc, char* argv[]) {
    mqtt::async_client client(ADDRESS, CLIENT_ID);

    // 设置回调函数
    client.set_callback(callback);

    mqtt::connect_options connOpts;
    connOpts.set_keep_alive_interval(20);
    connOpts.set_clean_session(true);

    try {
        mqtt::token_ptr conntok = client.connect(connOpts);

        conntok->wait();

        if (conntok->get_return_code() != mqtt::connect_return_code::RC_SUCCESS) {
            std::cout << "连接到MQTT服务器失败：" << conntok->get_return_code() << std::endl;
            return 1;
        }

        std::string topic { "test/topic" };
        mqtt::message_ptr pubmsg = mqtt::make_message(topic, "Hello, world!");
        pubmsg->set_qos(0);
        client.publish(pubmsg)->wait_for(std::chrono::seconds(10));
    } catch (const mqtt::exception& exc) {
        std::cerr << "连接到MQTT服务器失败：" << exc.what() << std::endl;
        return 1;
    }

    return 0;
}

服务端：

#include "mqtt/server.h"

const std::string ADDRESS { "tcp://localhost:1883" };

class custom_server_callback : public mqtt::callback {
public:
    void connected(const std::string& cause) override {
        std::cout << "连接到MQTT客户端：" << cause << std::endl;
    }

    void connection_lost(const std::string& cause) override {
        std::cout << "MQTT客户端连接断开：" << cause << std::endl;
    }

    void message_arrived(const std::string& topic, mqtt::message_ptr msg) override {
        std::cout << "收到MQTT消息：" << msg->to_string() << std::endl;
    }

    void delivery_complete(mqtt::delivery_token_ptr token) override {
        std::cout << "MQTT消息已发送：" << token->get_message_id() << std::endl;
    }
};

int main(int argc, char* argv[]) {
    mqtt::server server(ADDRESS, custom_server_callback());

    server.start();

    while (true) {
        std::this_thread::sleep_for(std::chrono::milliseconds(500));
    }

    return 0;
}

以上示例仅供参考，实际上，你需要根据你的具体需求来实现MQTT客户端和服务端。