publisher & receiver examples, better completion token examples

Reviewers: iljazovic, ivica

Reviewed By: ivica

Subscribers: miljen

Differential Revision: https://repo.mireo.local/D26582

example/publisher.cpp

@@ -0,0 +1,55 @@
+//[publisher
+#include <iostream>
+
+#include <boost/asio/co_spawn.hpp>
+#include <boost/asio/detached.hpp>
+#include <boost/asio/io_context.hpp>
+#include <boost/asio/use_awaitable.hpp>
+
+#include <boost/asio/ip/tcp.hpp>
+
+#include <async_mqtt5.hpp>
+
+namespace asio = boost::asio;
+
+asio::awaitable<void> client_publisher(asio::io_context& ioc) {
+	// Initialise the ``__Client__``, establish connection to the Broker over TCP.
+	async_mqtt5::mqtt_client<asio::ip::tcp::socket> client(ioc, "");
+
+	// Configure the ``__Client__``.
+	// It is mandatory to call brokers() and run() to configure the Brokers to connect to and start the Client.
+	client.brokers("mqtt.mireo.local", 1883) // Broker that we want to connect to. 1883 is the default TCP port.
+		.run(); // Start the client.
+
+	// Publish an Application Message with QoS 1.
+	auto [rc, props] = co_await client.async_publish<async_mqtt5::qos_e::at_least_once>(
+		"test/mqtt-test", "my application message",
+		async_mqtt5::retain_e::yes, async_mqtt5::publish_props {}, asio::use_awaitable
+	);
+	if (rc)
+		std::cout << "MQTT protocol error occurred: " << rc.message() << std::endl;
+
+	// Publish some more messages...
+
+	// After we are done with publishing all the messages, disconnect the Client.
+	// Alternatively, you can also use mqtt_client::cancel.
+	// Regardless, you should ensure all the operations are completed before disconnecting the Client.
+	co_await client.async_disconnect(
+		async_mqtt5::disconnect_rc_e::normal_disconnection, async_mqtt5::disconnect_props {}, asio::use_awaitable
+	);
+
+	co_return;
+}
+
+int main() {
+	// Initialise execution context.
+	asio::io_context ioc;
+
+	// Spawn the coroutine.
+	asio::co_spawn(ioc.get_executor(), client_publisher(ioc), asio::detached);
+
+	// Start the execution.
+	ioc.run();
+}
+
+//]