// Copyright (C) 2018 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GFDL-1.3-no-invariants-only

/*!
    \example simpleclient
    \examplecategory {Connectivity}
    \title Simple MQTT Client
    \ingroup qtmqtt-examples
    \brief Creating a minimalistic telemetry application.

    \image simpleclient.png
           {MQTT client with Host, Port, Protocol fields, WebSockets and Secure
           options, Topic and Message inputs, and log showing state changes}

    \e {Simple MQTT Client} demonstrates how to create a minimalistic client
    application.

    To use the application, you first specify a Host, a Port, Secure on/off,
    WebSockets on/off, and Protocol. Then click on connect. Afterward you can
    subscribe to a topic and send a message, which you will also receive.
    You may also run the application twice. Publish in one and Subscribe in
    the other, and the messages shall be transmitted.

    \section1 simpleclient Options
    \list
        \li Host - you may use test.mosquitto.org or broker.hivemq.com
        \li Port - port to connect to, will depend on WebSockets selection and Secure selection
        \li WebSockets - you may specify: selected (enabled) or not selected (disabled)
        \li Secure - you may specify: selected (enabled) or not selected (disabled)
        \li Protocol - you may specify
        \list
             \li mqtt 3.1
             \li mqtt 3.1.1
             \li mqtt 5.0
        \endlist
        \li Topic - A topic to publish or subscribe to
        \li Message - A message to send on the topic if you are publishing
    \endlist

    \section1 Connection Settings
    These are the usual combinations, and will work with test.mosquitto.org.
    For broker.hivemq.com check the information in the links. Note that if
    Secure is enabled it might be necessary to install certificates on the
    computer. It might also be necessary to add the certificate to the mqtt
    client in code.

    \section1
    \list
        \li Port 1883, Secure=disabled, WebSockets=disabled - mqtt over tcp
        \li Port 8883, Secure=enabled,  WebSockets=disabled - mqtt over ssl
        \li Port 8080, Secure=disabled, WebSockets=enabled  - mqtt over websockets
        \li Port 8081, Secure=enabled,  WebSockets=enabled  - mqtt over secure websockets
    \endlist

    For more information about the brokers see:
    \list
        \li \l {https://test.mosquitto.org}
        \li \l {https://broker.hivemq.com}
        \li \l {https://www.hivemq.com/mqtt/public-mqtt-broker}
    \endlist

    \note Port numbers 1883 and 8080 are not encrypted, and therefore they are
    suitable only for development and testing purposes. In production, always
    use encrypted connections.

    \note WebAssembly only supports WebSockets enabled.

    \section1 Creating a Client

    First, we use the QMqttClient class to create an MQTT client. The class
    provides properties for setting a unique client ID as well as the broker
    host name and port to connect to:

    \quotefromfile simpleclient/mainwindow.cpp
    \skipto m_client
    \printuntil setPort

    We do not set the client ID, and therefore it will be automatically
    generated for us.

    Next, we connect to QMqttClient::messageReceived() to receive all messages
    sent to the broker:

    \skipto messageReceived
    \printuntil }

    When users subscribe to topics in the client, we call
    QMqttClient::subscribe() on the specified topic:

    \skipto on_buttonSubscribe_clicked
    \printuntil }

    In this example, we subscribe to all topics. For more information about
    how to receive messages on particular topics, see the
    \l {MQTT Subscriptions} example.

    For an example of how to use the QMqttClient class in a Qt Quick
    application, see \l {Qt Quick Subscription}.
*/
