WebSockets MQTT Subscription Example | Qt MQTT 6.4.1

- Qt 6.4
- Qt MQTT
- Qt MQTT Examples
- WebSockets MQTT Subscription Example
- Qt 6.4.1 Reference Documentation

# WebSockets MQTT Subscription Example

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

     #include "websocketiodevice.h"

     #include <QtCore/QDebug>

     WebSocketIODevice::WebSocketIODevice(QObject *parent)
         : QIODevice(parent)
     {
         connect(&m_socket, &QWebSocket::connected, this, &WebSocketIODevice::onSocketConnected);
         connect(&m_socket, &QWebSocket::binaryMessageReceived, this, &WebSocketIODevice::handleBinaryMessage);
     }

     bool WebSocketIODevice::open(QIODevice::OpenMode mode)
     {
         // Cannot use an URL because of missing sub protocol support
         // Have to use QNetworkRequest, see QTBUG-38742
         QNetworkRequest request;
         request.setUrl(m_url);
         request.setRawHeader("Sec-WebSocket-Protocol", m_protocol.constData());

         m_socket.open(request);

         return QIODevice::open(mode);
     }

     void WebSocketIODevice::close()
     {
         m_socket.close();
         QIODevice::close();
     }

     qint64 WebSocketIODevice::readData(char *data, qint64 maxlen)
     {
         qint64 bytesToRead = qMin(maxlen, (qint64)m_buffer.size());
         memcpy(data, m_buffer.constData(), bytesToRead);
         m_buffer = m_buffer.right(m_buffer.size() - bytesToRead);
         return bytesToRead;
     }

     qint64 WebSocketIODevice::writeData(const char *data, qint64 len)
     {
         QByteArray msg(data, len);
         const int length = m_socket.sendBinaryMessage(msg);
         return length;
     }

     void WebSocketIODevice::setUrl(const QUrl &url)
     {
         m_url = url;
     }

     void WebSocketIODevice::setProtocol(const QByteArray &data)
     {
         m_protocol = data;
     }

     void WebSocketIODevice::handleBinaryMessage(const QByteArray &msg)
     {
         m_buffer.append(msg);
         emit readyRead();
     }

     void WebSocketIODevice::onSocketConnected()
     {
         emit socketConnected();
     }