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// Copyright (C) 2018 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GFDL-1.3-no-invariants-only
/*!
\example websocketsubscription
\examplecategory {Connectivity}
\title WebSockets MQTT Subscription
\ingroup qtmqtt-examples
\brief Combining an MQTT client with a web socket connection.
\e {WebSockets MQTT Subscription} shows how to design a custom
QIODevice to combine a \l {Qt WebSockets}{web socket} connection with
QMqttClient.
\section1 Creating a Custom QIODevice
The new custom device, \c WebSocketIODevice, has to be a subclass of
\l QIODevice:
\quotefromfile websocketsubscription/websocketiodevice.h
\skipto WebSocketIODevice
\printuntil }
\section1 Designing a Class to Manage the Connection and Subscription
\c WebSocketIODevice will be a private member of the \c ClientSubscription
class alongside the QMqttClient and the QMqttSubscription:
\quotefromfile websocketsubscription/clientsubscription.h
\skipto private
\printuntil m_version
\section1 Subscribing to and Receiving Messages
The main logic is implemented in the \c connectAndSubscribe() method of the
\c ClientSubscription class. You need to verify that the web socket has
successfully connected before you can initialize an MQTT connection over
it. After the MQTT connection has been established, the QMqttClient can
subscribe to the topic. If the subscription is successful, the
QMqttSubscription can be used to receive messages from the subscribed topic
that will be handled by the \c handleMessage() method of the
\c ClientSubscription class.
\quotefromfile websocketsubscription/clientsubscription.cpp
\skipto connectAndSubscribe
\printuntil Could
\printuntil }
*/
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