mirror of
https://github.com/eclipse/paho.mqtt.cpp.git
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114 lines
3.1 KiB
C++
114 lines
3.1 KiB
C++
// async_consume.cpp
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//
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// This is a Paho MQTT C++ client, sample application.
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//
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// This application is an MQTT consumer/subscriber using the C++
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// asynchronous client interface, employing the to receive messages
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// and status updates.
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//
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// The sample demonstrates:
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// - Connecting to an MQTT server/broker.
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// - Subscribing to a topic
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// - Receiving messages through the synchronous queuing API
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//
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/*******************************************************************************
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* Copyright (c) 2013-2023 Frank Pagliughi <fpagliughi@mindspring.com>
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*
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* All rights reserved. This program and the accompanying materials
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* are made available under the terms of the Eclipse Public License v2.0
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* and Eclipse Distribution License v1.0 which accompany this distribution.
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*
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* The Eclipse Public License is available at
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* http://www.eclipse.org/legal/epl-v20.html
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* and the Eclipse Distribution License is available at
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* http://www.eclipse.org/org/documents/edl-v10.php.
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*
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* Contributors:
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* Frank Pagliughi - initial implementation and documentation
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*******************************************************************************/
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#include <iostream>
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#include <cstdlib>
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#include <string>
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#include <cstring>
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#include <cctype>
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#include <thread>
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#include <chrono>
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#include "mqtt/async_client.h"
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using namespace std;
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const string SERVER_ADDRESS { "mqtt://localhost:1883" };
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const string CLIENT_ID { "paho_cpp_async_consume" };
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const string TOPIC { "hello" };
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const int QOS = 1;
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/////////////////////////////////////////////////////////////////////////////
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int main(int argc, char* argv[])
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{
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mqtt::async_client cli(SERVER_ADDRESS, CLIENT_ID);
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auto connOpts = mqtt::connect_options_builder()
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.clean_session(false)
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.finalize();
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try {
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// Start consumer before connecting to make sure to not miss messages
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cli.start_consuming();
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// Connect to the server
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cout << "Connecting to the MQTT server..." << flush;
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auto tok = cli.connect(connOpts);
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// Getting the connect response will block waiting for the
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// connection to complete.
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auto rsp = tok->get_connect_response();
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// If there is no session present, then we need to subscribe, but if
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// there is a session, then the server remembers us and our
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// subscriptions.
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if (!rsp.is_session_present())
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cli.subscribe(TOPIC, QOS)->wait();
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cout << "OK" << endl;
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// Consume messages
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// This just exits if the client is disconnected.
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// (See some other examples for auto or manual reconnect)
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cout << "Waiting for messages on topic: '" << TOPIC << "'" << endl;
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while (true) {
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auto msg = cli.consume_message();
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if (!msg) break;
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cout << msg->get_topic() << ": " << msg->to_string() << endl;
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}
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// If we're here, the client was almost certainly disconnected.
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// But we check, just to make sure.
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if (cli.is_connected()) {
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cout << "\nShutting down and disconnecting from the MQTT server..." << flush;
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cli.unsubscribe(TOPIC)->wait();
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cli.stop_consuming();
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cli.disconnect()->wait();
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cout << "OK" << endl;
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}
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else {
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cout << "\nClient was disconnected" << endl;
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}
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}
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catch (const mqtt::exception& exc) {
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cerr << "\n " << exc << endl;
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return 1;
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}
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return 0;
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}
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