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This example illustrates the process of setting up the Client to connect to the Broker via Websocket/TCP and publish a "Hello World!" message.
#include <boost/mqtt5/logger.hpp> #include <boost/mqtt5/mqtt_client.hpp> #include <boost/mqtt5/types.hpp> #include <boost/mqtt5/websocket.hpp> // WebSocket traits #include <boost/asio/detached.hpp> #include <boost/asio/io_context.hpp> #include <boost/asio/ip/tcp.hpp> #include <boost/beast/websocket.hpp> #include <iostream> #include <string> struct config { std::string brokers = "broker.hivemq.com/mqtt"; // Path example: localhost/mqtt uint16_t port = 8000; // 8083 is the default Webscoket/TCP MQTT port. However, HiveMQ's public broker uses 8000 instead. 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 WebSocket/TCP 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::beast::websocket::stream<boost::asio::ip::tcp::socket>, std::monostate, boost::mqtt5::logger > client(ioc, {}, boost::mqtt5::logger(boost::mqtt5::log_level::info)); // If you want to use the Client without logging, initialise it with the following line instead. //boost::mqtt5::mqtt_client<boost::beast::websocket::stream<boost::asio::ip::tcp::socket>> client(ioc); 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. client.async_publish<boost::mqtt5::qos_e::at_most_once>( "boost-mqtt5/test", "Hello world!", boost::mqtt5::retain_e::no, boost::mqtt5::publish_props {}, [&client](boost::mqtt5::error_code ec) { std::cout << ec.message() << std::endl; client.async_disconnect(boost::asio::detached); } ); ioc.run(); }