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Alternate text (alt text) improves the documentation experience for screen readers and for other accessibility tools. Task-number: QTBUG-135098 Pick-to: 6.11 Change-Id: Ia1793ff3e0bacd8cfdad2e8c04725a5093ed30aa Reviewed-by: David Boddie <david.boddie@qt.io>
100 lines
3.8 KiB
Plaintext
100 lines
3.8 KiB
Plaintext
// Copyright (C) 2018 The Qt Company Ltd.
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// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GFDL-1.3-no-invariants-only
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/*!
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\example simpleclient
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\examplecategory {Connectivity}
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\title Simple MQTT Client
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\ingroup qtmqtt-examples
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\brief Creating a minimalistic telemetry application.
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\image simpleclient.png
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{MQTT client with Host, Port, Protocol fields, WebSockets and Secure
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options, Topic and Message inputs, and log showing state changes}
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\e {Simple MQTT Client} demonstrates how to create a minimalistic client
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application.
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To use the application, you first specify a Host, a Port, Secure on/off,
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WebSockets on/off, and Protocol. Then click on connect. Afterward you can
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subscribe to a topic and send a message, which you will also receive.
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You may also run the application twice. Publish in one and Subscribe in
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the other, and the messages shall be transmitted.
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\section1 simpleclient Options
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\list
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\li Host - you may use test.mosquitto.org or broker.hivemq.com
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\li Port - port to connect to, will depend on WebSockets selection and Secure selection
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\li WebSockets - you may specify: selected (enabled) or not selected (disabled)
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\li Secure - you may specify: selected (enabled) or not selected (disabled)
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\li Protocol - you may specify
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\list
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\li mqtt 3.1
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\li mqtt 3.1.1
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\li mqtt 5.0
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\endlist
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\li Topic - A topic to publish or subscribe to
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\li Message - A message to send on the topic if you are publishing
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\endlist
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\section1 Connection Settings
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These are the usual combinations, and will work with test.mosquitto.org.
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For broker.hivemq.com check the information in the links. Note that if
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Secure is enabled it might be necessary to install certificates on the
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computer. It might also be necessary to add the certificate to the mqtt
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client in code.
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\section1
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\list
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\li Port 1883, Secure=disabled, WebSockets=disabled - mqtt over tcp
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\li Port 8883, Secure=enabled, WebSockets=disabled - mqtt over ssl
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\li Port 8080, Secure=disabled, WebSockets=enabled - mqtt over websockets
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\li Port 8081, Secure=enabled, WebSockets=enabled - mqtt over secure websockets
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\endlist
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For more information about the brokers see:
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\list
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\li \l {https://test.mosquitto.org}
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\li \l {https://broker.hivemq.com}
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\li \l {https://www.hivemq.com/mqtt/public-mqtt-broker}
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\endlist
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\note Port numbers 1883 and 8080 are not encrypted, and therefore they are
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suitable only for development and testing purposes. In production, always
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use encrypted connections.
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\note WebAssembly only supports WebSockets enabled.
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\section1 Creating a Client
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First, we use the QMqttClient class to create an MQTT client. The class
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provides properties for setting a unique client ID as well as the broker
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host name and port to connect to:
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\quotefromfile simpleclient/mainwindow.cpp
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\skipto m_client
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\printuntil setPort
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We do not set the client ID, and therefore it will be automatically
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generated for us.
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Next, we connect to QMqttClient::messageReceived() to receive all messages
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sent to the broker:
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\skipto messageReceived
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\printuntil }
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When users subscribe to topics in the client, we call
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QMqttClient::subscribe() on the specified topic:
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\skipto on_buttonSubscribe_clicked
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\printuntil }
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In this example, we subscribe to all topics. For more information about
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how to receive messages on particular topics, see the
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\l {MQTT Subscriptions} example.
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For an example of how to use the QMqttClient class in a Qt Quick
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application, see \l {Qt Quick Subscription}.
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*/
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