paho.mqtt.cpp/examples/ssl_publish.cpp

// ssl_publish.cpp
//
// This is a Paho MQTT C++ client, sample application.
//
// It's an example of how to connect to an MQTT broker securely, and then
// send messages as an MQTT publisher using the C++ asynchronous client
// interface.
//
// The sample demonstrates:
//  - Connecting to an MQTT server/broker securely
//  - Setting SSL/TLS options
//  - Last will and testament
//  - Publishing messages
//  - Using asynchronous tokens
//  - Implementing callbacks and action listeners
//
// We can test this using mosquitto configured with certificates in the
// Paho C library. The C library has an SSL/TSL test suite, and we can use
// that to test:
//     $ cd paho.mqtt.c
//     $ mosquitto -c test/tls-testing/mosquitto.conf
//
// Then use the files "test-root-ca.crt" and "client.pem" from the
// test/ssl directory (paho.mqtt.c/test/ssl) for the trust store and
// key_store, respectively, for this program.
//

/*******************************************************************************
 * Copyright (c) 2013-2023 Frank Pagliughi <fpagliughi@mindspring.com>
 *
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v2.0
 * and Eclipse Distribution License v1.0 which accompany this distribution.
 *
 * The Eclipse Public License is available at
 *    http://www.eclipse.org/legal/epl-v20.html
 * and the Eclipse Distribution License is available at
 *   http://www.eclipse.org/org/documents/edl-v10.php.
 *
 * Contributors:
 *    Frank Pagliughi - initial implementation and documentation
 *******************************************************************************/

#include <iostream>
#include <fstream>
#include <cstdlib>
#include <string>
#include <chrono>
#include <cstring>
#include "mqtt/async_client.h"

const std::string DFLT_SERVER_ADDRESS	{ "mqtts://localhost:18884" };
const std::string DFLT_CLIENT_ID		{ "ssl_publish_cpp" };

const std::string KEY_STORE				{ "client.pem" };
const std::string TRUST_STORE			{ "test-root-ca.crt" };

const std::string LWT_TOPIC				{ "events/disconnect" };
const std::string LWT_PAYLOAD			{ "Last will and testament." };

const int  QOS = 1;
const auto TIMEOUT = std::chrono::seconds(10);

/////////////////////////////////////////////////////////////////////////////

/**
 * A callback class for use with the main MQTT client.
 */
class callback : public virtual mqtt::callback
{
public:
	void connection_lost(const std::string& cause) override {
		std::cout << "\nConnection lost" << std::endl;
		if (!cause.empty())
			std::cout << "\tcause: " << cause << std::endl;
	}

	void delivery_complete(mqtt::delivery_token_ptr tok) override {
		std::cout << "\tDelivery complete for token: "
			<< (tok ? tok->get_message_id() : -1) << std::endl;
	}
};

/////////////////////////////////////////////////////////////////////////////

using namespace std;

int main(int argc, char* argv[])
{
	string	address  = (argc > 1) ? string(argv[1]) : DFLT_SERVER_ADDRESS,
			clientID = (argc > 2) ? string(argv[2]) : DFLT_CLIENT_ID;

	// Note that we don't actually need to open the trust or key stores.
	// We just need a quick, portable way to check that they exist.
	{
		ifstream tstore(TRUST_STORE);
		if (!tstore) {
			cerr << "The trust store file does not exist: " << TRUST_STORE << endl;
			cerr << "  Get a copy from \"paho.mqtt.c/test/ssl/test-root-ca.crt\"" << endl;;
			return 1;
		}

		ifstream kstore(KEY_STORE);
		if (!kstore) {
			cerr << "The key store file does not exist: " << KEY_STORE << endl;
			cerr << "  Get a copy from \"paho.mqtt.c/test/ssl/client.pem\"" << endl;
			return 1;
		}
    }

	cout << "Initializing for server '" << address << "'..." << endl;
	mqtt::async_client client(address, clientID);

	callback cb;
	client.set_callback(cb);

	// Build the connect options, including SSL and a LWT message.

	auto sslopts = mqtt::ssl_options_builder()
					   .trust_store(TRUST_STORE)
					   .key_store(KEY_STORE)
					   .error_handler([](const std::string& msg) {
						   std::cerr << "SSL Error: " << msg << std::endl;
					   })
					   .finalize();

	auto willmsg = mqtt::message(LWT_TOPIC, LWT_PAYLOAD, QOS, true);

	auto connopts = mqtt::connect_options_builder()
					    .user_name("testuser")
					    .password("testpassword")
					    .will(std::move(willmsg))
						.ssl(std::move(sslopts))
						.finalize();

	cout << "  ...OK" << endl;

	try {
		// Connect using SSL/TLS

		cout << "\nConnecting..." << endl;
		mqtt::token_ptr conntok = client.connect(connopts);
		cout << "Waiting for the connection..." << endl;
		conntok->wait();
		cout << "  ...OK" << endl;

		// Send a message

		cout << "\nSending message..." << endl;
		auto msg = mqtt::make_message("hello", "Hello secure C++ world!", QOS, false);
		client.publish(msg)->wait_for(TIMEOUT);
		cout << "  ...OK" << endl;

		// Disconnect

		cout << "\nDisconnecting..." << endl;
		client.disconnect()->wait();
		cout << "  ...OK" << endl;
	}
	catch (const mqtt::exception& exc) {
		cerr << exc.what() << endl;
		return 1;
	}

 	return 0;
}