//[receiver #include #include #include #include #include #include #include #ifdef BOOST_ASIO_HAS_CO_AWAIT namespace asio = boost::asio; asio::awaitable client_receiver(asio::io_context& ioc) { // Initialise the ``__Client__``, establish connection to the Broker over TCP. async_mqtt5::mqtt_client client(ioc, ""); // Configure the``__Client__``. // It is mandatory to call brokers() and async_run() to configure the Brokers to connect to and start the Client. client.brokers("mqtt.broker", 1883) // Broker that we want to connect to. 1883 is the default TCP port. .async_run(asio::detached); // Start the client. // Configure the request to subscribe to a Topic. async_mqtt5::subscribe_topic sub_topic = async_mqtt5::subscribe_topic { "test/mqtt-test", async_mqtt5::subscribe_options { async_mqtt5::qos_e::exactly_once, // All messages will arrive at QoS 2. async_mqtt5::subscribe_options::no_local_e::no, // Forward message from Clients with same ID. async_mqtt5::subscribe_options::retain_as_published_e::retain, // Keep the original RETAIN flag. async_mqtt5::subscribe_options::retain_handling_e::send // Send retained messages when the subscription is established. } }; // Subscribe to a single Topic. auto [sub_codes, sub_props] = co_await client.async_subscribe( sub_topic, async_mqtt5::subscribe_props {}, asio::use_awaitable ); // Note: you can subscribe to multiple Topics in one mqtt_client::async_subscribe call. // std::vector sub_codes contain the result of the subscribe action for every Topic. // Before attempting to receive an Application Message from the Topic we just subscribed to, // it is advisable to verify that the subscription succeeded. // It is not recommended to call mqtt_client::async_receive if you do not have any // Subscription established as the corresponding handler will never be invoked. if (!sub_codes[0]) auto [topic, payload, publish_props] = co_await client.async_receive(asio::use_awaitable); // Receive more messages... // Unsubscribe from the Topic. // Similar to mqtt_client::async_subscribe call, std::vector unsub_codes contain // the result of the unsubscribe action for every Topic. auto [unsub_codes, unsub_props] = co_await client.async_unsubscribe( "test/mqtt-test", async_mqtt5::unsubscribe_props {}, asio::use_awaitable ); // Note: you can unsubscribe from multiple Topics in one mqtt_client::async_unsubscribe call. // Disconnect the Client. co_await client.async_disconnect( async_mqtt5::disconnect_rc_e::disconnect_with_will_message, async_mqtt5::disconnect_props {}, asio::use_awaitable ); co_return; } int main() { // Initialise execution context. asio::io_context ioc; // Spawn the coroutine. co_spawn(ioc, client_receiver(ioc), asio::detached); // Start the execution. ioc.run(); } //] #endif