ubuntu mqtt客户端

在Ubuntu上，你可以使用 Eclipse Paho 这个 MQTT 客户端库来实现 MQTT 客户端。

以下是在 Ubuntu 上安装 Paho MQTT 客户端库的步骤：

1. 打开终端并更新本地软件包列表：

sudo apt-get update

2. 安装 Paho MQTT 客户端库：

sudo apt-get install libssl-dev libcrypto++-dev libssl-doc
sudo apt-get install libpaho-mqtt-dev

3. 编写一个 MQTT 客户端代码，例如：

#include <iostream>
#include <cstring>
#include <cstdlib>
#include <csignal>
#include "mqtt/async_client.h"

const std::string SERVER_ADDRESS { "tcp://localhost:1883" };
const std::string CLIENT_ID { "async_subcribe_cpp" };

class callback : public virtual mqtt::callback
{
    void connection_lost(const std::string& cause) override
    {
        std::cout << "\nConnection lost" << std::endl;
        if (!cause.empty())
            std::cout << "\tcause: " << cause << std::endl;
    }

    void delivery_complete(mqtt::delivery_token_ptr token) override {}

    mqtt::subscription_promise* sub_promise_;

public:
    callback(mqtt::subscription_promise* sub_promise)
            : sub_promise_(sub_promise) {}

    void connected(const std::string& cause) override
    {
        std::cout << "Connection success" << std::endl;
        sub_promise_->set_value(0);
    }

    void message_arrived(mqtt::const_message_ptr msg) override
    {
        std::cout << "Message arrived" << std::endl;
        std::cout << "\ttopic: '" << msg->get_topic() << "'" << std::endl;
        std::cout << "\tpayload: '" << msg->to_string() << "'\n" << std::endl;
    }
};

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

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

    mqtt::subscription_promise sub_promise;
    mqtt::subscription_options subOpts;
    subOpts.set_no_local(true);
    subOpts.set_qos(1);

    callback cb(&sub_promise);
    client.set_callback(cb);

    try {
        std::cout << "Connecting to the MQTT server..." << std::endl;
        mqtt::token_ptr conntok = client.connect(connOpts);
        conntok->wait();
        std::cout << "Connected" << std::endl;

        mqtt::token_ptr subtok = client.subscribe("test", subOpts);
        subtok->wait();
        std::cout << "Subscribed to topic 'test'" << std::endl;

        sub_promise.get_future().wait();

        while (true) {}
    }
    catch (const mqtt::exception& exc) {
        std::cerr << "MQTT Exception: " << exc.what() << std::endl;
        return 1;
    }

    return 0;
}

4. 编译并运行 MQTT 客户端代码：

g++ -o mqtt_client mqtt_client.cpp -lpaho-mqtt3a -lpaho-mqttpp3
./mqtt_client

以上代码实现了一个 MQTT 订阅者客户端，它将连接到本地主机上的 MQTT 代理，并订阅名为“test”的主题。当有新消息到达“test”主题时，客户端将输出消息的主题和有效负载。