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

#include <iostream>
#include <string>

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

#include <async_mqtt5/logger.hpp>
#include <async_mqtt5/mqtt_client.hpp>
#include <async_mqtt5/reason_codes.hpp>
#include <async_mqtt5/types.hpp>

struct config {
	std::string brokers = "broker.hivemq.com";
	uint16_t port = 1883;
	std::string client_id = "async_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.
	async_mqtt5::mqtt_client<
		boost::asio::ip::tcp::socket, std::monostate /* TlsContext */, async_mqtt5::logger
	> client(ioc, {} /* tls_context */, async_mqtt5::logger(async_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<async_mqtt5::qos_e::exactly_once>(
			"async-mqtt5/test", "Hello world!",
			async_mqtt5::retain_e::no, async_mqtt5::publish_props {},
			[i](async_mqtt5::error_code ec, async_mqtt5::reason_code rc, async_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](async_mqtt5::error_code, int) {
		client.async_disconnect(boost::asio::detached);
	});

	ioc.run();
}