WebSockets MQTT Subscription Example

 // Copyright (C) 2017 The Qt Company Ltd.
 // SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause

 #ifndef WEBSOCKETIODEVICE_H
 #define WEBSOCKETIODEVICE_H

 #include <QtCore/QIODevice>
 #include <QtWebSockets/QWebSocket>

 class WebSocketIODevice : public QIODevice
 {
     Q_OBJECT
 public:
     WebSocketIODevice(QObject *parent = nullptr);

     bool open(OpenMode mode) override;
     void close() override;

     qint64 readData(char *data, qint64 maxlen) override;
     qint64 writeData(const char *data, qint64 len) override;

     void setUrl(const QUrl &url);
     void setProtocol(const QByteArray &data);
 Q_SIGNALS:
     void socketConnected();

 public slots:
     void handleBinaryMessage(const QByteArray &msg);
     void onSocketConnected();

 private:
     QByteArray m_protocol;
     QByteArray m_buffer;
     QWebSocket m_socket;
     QUrl m_url;
 };

 #endif // WEBSOCKETIODEVICE_H