This example illustrates the process of setting up the Client to connect to the Broker via TCP/IP and publish a "Hello World!" message.

#include <iostream>
#include <string>

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

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

struct config {
	std::string brokers = "broker.hivemq.com";
	uint16_t port = 1883; // 1883 is the default TCP MQTT port.
	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));

	// If you want to use the Client without logging, initialise it with the following line instead.
	//async_mqtt5::mqtt_client<boost::asio::ip::tcp::socket> client(ioc);

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

	client.async_publish<async_mqtt5::qos_e::at_most_once>(
		"async-mqtt5/test", "Hello world!",
		async_mqtt5::retain_e::yes, async_mqtt5::publish_props {},
		[&client](async_mqtt5::error_code ec) {
			std::cout << ec.message() << std::endl;

			// Disconnnect the Client.
			client.async_disconnect(boost::asio::detached);
		}
	);

	ioc.run();
}