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# dialog.cpp Example File
network/loopback/dialog.cpp

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        ** Copyright (C) 2004-2006 Trolltech ASA. All rights reserved.
        **
        ** This file is part of the documentation of the Qt Toolkit.
        **
        ** This file may be used under the terms of the GNU General Public
        ** License version 2.0 as published by the Free Software Foundation
        ** and appearing in the file LICENSE.GPL included in the packaging of
        ** this file.  Please review the following information to ensure GNU
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        ** review the following information:
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        ** WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
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        #include <QtGui>
        #include <QtNetwork>

        #include "dialog.h"

        static const int TotalBytes = 50 * 1024 * 1024;
        static const int PayloadSize = 65536;

        Dialog::Dialog(QWidget *parent)
            : QDialog(parent)
        {
            clientProgressBar = new QProgressBar;
            clientStatusLabel = new QLabel(tr("Client ready"));
            serverProgressBar = new QProgressBar;
            serverStatusLabel = new QLabel(tr("Server ready"));

            startButton = new QPushButton(tr("&Start"));
            quitButton = new QPushButton(tr("&Quit"));

            connect(startButton, SIGNAL(clicked()), this, SLOT(start()));
            connect(quitButton, SIGNAL(clicked()), this, SLOT(close()));
            connect(&tcpServer, SIGNAL(newConnection()),
                    this, SLOT(acceptConnection()));
            connect(&tcpClient, SIGNAL(connected()), this, SLOT(startTransfer()));
            connect(&tcpClient, SIGNAL(bytesWritten(qint64)),
                    this, SLOT(updateClientProgress(qint64)));
            connect(&tcpClient, SIGNAL(error(QAbstractSocket::SocketError)),
                    this, SLOT(displayError(QAbstractSocket::SocketError)));

            QHBoxLayout *buttonLayout = new QHBoxLayout;
            buttonLayout->addStretch(1);
            buttonLayout->addWidget(startButton);
            buttonLayout->addWidget(quitButton);

            QVBoxLayout *mainLayout = new QVBoxLayout;
            mainLayout->addWidget(clientProgressBar);
            mainLayout->addWidget(clientStatusLabel);
            mainLayout->addWidget(serverProgressBar);
            mainLayout->addWidget(serverStatusLabel);
            mainLayout->addLayout(buttonLayout);
            setLayout(mainLayout);

            setWindowTitle(tr("Loopback"));
        }

        void Dialog::start()
        {
            startButton->setEnabled(false);

            QApplication::setOverrideCursor(Qt::WaitCursor);

            bytesWritten = 0;
            bytesReceived = 0;

            while (!tcpServer.isListening() && !tcpServer.listen()) {
                int ret = QMessageBox::critical(this, tr("Loopback"),
                                                tr("Unable to start the test: %1.")
                                                .arg(tcpServer.errorString()),
                                                QMessageBox::Retry,
                                                QMessageBox::Cancel);
                if (ret == QMessageBox::Cancel)
                    return;
            }

            serverStatusLabel->setText(tr("Listening"));
            clientStatusLabel->setText(tr("Connecting"));
            tcpClient.connectToHost(QHostAddress::LocalHost, tcpServer.serverPort());
        }

        void Dialog::acceptConnection()
        {
            tcpServerConnection = tcpServer.nextPendingConnection();
            connect(tcpServerConnection, SIGNAL(readyRead()),
                    this, SLOT(updateServerProgress()));
            connect(tcpServerConnection, SIGNAL(error(QAbstractSocket::SocketError)),
                    this, SLOT(displayError(QAbstractSocket::SocketError)));

            serverStatusLabel->setText(tr("Accepted connection"));
            tcpServer.close();
        }

        void Dialog::startTransfer()
        {
            bytesToWrite = TotalBytes - (int)tcpClient.write(QByteArray(PayloadSize, '@'));
            clientStatusLabel->setText(tr("Connected"));
        }

        void Dialog::updateServerProgress()
        {
            bytesReceived += (int)tcpServerConnection->bytesAvailable();
            tcpServerConnection->readAll();

            serverProgressBar->setMaximum(TotalBytes);
            serverProgressBar->setValue(bytesReceived);
            serverStatusLabel->setText(tr("Received %1MB")
                                       .arg(bytesReceived / (1024 * 1024)));

            if (bytesReceived == TotalBytes) {
                tcpServerConnection->close();
                startButton->setEnabled(true);
                QApplication::restoreOverrideCursor();
            }
        }

        void Dialog::updateClientProgress(qint64 numBytes)
        {
            bytesWritten += (int)numBytes;
            if (bytesToWrite > 0)
                bytesToWrite -= (int)tcpClient.write(QByteArray(qMin(bytesToWrite, PayloadSize), '@'));

            clientProgressBar->setMaximum(TotalBytes);
            clientProgressBar->setValue(bytesWritten);
            clientStatusLabel->setText(tr("Sent %1MB")
                                       .arg(bytesWritten / (1024 * 1024)));
        }

        void Dialog::displayError(QAbstractSocket::SocketError socketError)
        {
            if (socketError == QTcpSocket::RemoteHostClosedError)
                return;

            QMessageBox::information(this, tr("Network error"),
                                     tr("The following error occurred: %1.")
                                     .arg(tcpClient.errorString()));

            tcpClient.close();
            tcpServer.close();
            clientProgressBar->reset();
            serverProgressBar->reset();
            clientStatusLabel->setText(tr("Client ready"));
            serverStatusLabel->setText(tr("Server ready"));
            startButton->setEnabled(true);
            QApplication::restoreOverrideCursor();
        }