| Home | Libraries | People | FAQ | More

### The multiflight Client

This example shows how to use ``mqtt_client`` to simultaneously dispatch multiple requests.

    #include <boost/mqtt5/logger.hpp>
    #include <boost/mqtt5/mqtt_client.hpp>
    #include <boost/mqtt5/reason_codes.hpp>
    #include <boost/mqtt5/types.hpp>

    #include <boost/asio/detached.hpp>
    #include <boost/asio/io_context.hpp>
    #include <boost/asio/ip/tcp.hpp>
    #include <boost/asio/signal_set.hpp>

    #include <iostream>
    #include <string>

    struct config {
        std::string brokers = "broker.hivemq.com";
        uint16_t port = 1883;
        std::string client_id = "boost_mqtt5_tester";
    };

    int main(int argc, char** argv) {
        config cfg;

        if (argc == 4) {
            cfg.brokers = argv[1];
            cfg.port = uint16_t(std::stoi(argv[2]));
            cfg.client_id = argv[3];
        }

        boost::asio::io_context ioc;

        // Construct the Client with boost::asio::ip::tcp::socket as the underlying stream and enabled logging.
        // Since we are not establishing a secure connection, set the TlsContext template parameter to std::monostate.
        boost::mqtt5::mqtt_client<
            boost::asio::ip::tcp::socket, std::monostate /* TlsContext */, boost::mqtt5::logger
        > client(ioc, {} /* tls_context */, boost::mqtt5::logger(boost::mqtt5::log_level::info));

        client.brokers(cfg.brokers, cfg.port) // Broker that we want to connect to.
            .credentials(cfg.client_id) // Set the Client Identifier. (optional)
            .async_run(boost::asio::detached); // Start the client.

        // Publish with QoS 2 five times in a row without waiting for the handler
        // of the previous async_publish call to be invoked.
        for (auto i = 1; i <= 5; ++i)
            client.async_publish<boost::mqtt5::qos_e::exactly_once>(
                "boost-mqtt5/test", "Hello world!",
                boost::mqtt5::retain_e::no, boost::mqtt5::publish_props {},
                [i](boost::mqtt5::error_code ec, boost::mqtt5::reason_code rc, boost::mqtt5::pubcomp_props) {
                    std::cout << "Publish number " << i << " completed with: " << std::endl;
                    std::cout << "\t ec: " << ec.message() << std::endl;
                    std::cout << "\t rc: " << rc.message() << std::endl;
                }
            );

        // We can stop the Client by using signals.
        boost::asio::signal_set signals(ioc, SIGINT, SIGTERM);
        signals.async_wait([&client](boost::mqtt5::error_code, int) {
            client.async_disconnect(boost::asio::detached);
        });

        ioc.run();
    }