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

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     ** General Public License version 2.1 as published by the Free Software
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     ** packaging of this file.  Please review the following information to
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     ** Alternatively, this file may be used under the terms of the GNU
     ** General Public License version 3.0 as published by the Free Software
     ** Foundation and appearing in the file LICENSE.GPL included in the
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     #include <QtGui>
     #include <QtNetwork>

     #include "dialog.h"

     #if !defined(Q_OS_WINCE) && !defined(Q_OS_SYMBIAN)
     static const int TotalBytes = 50 * 1024 * 1024;
     #else
     static const int TotalBytes = 5 * 1024 * 1024;
     #endif
     static const int PayloadSize = 64 * 1024; // 64 KB

     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"));

         buttonBox = new QDialogButtonBox;
         buttonBox->addButton(startButton, QDialogButtonBox::ActionRole);
         buttonBox->addButton(quitButton, QDialogButtonBox::RejectRole);

         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)));

         QVBoxLayout *mainLayout = new QVBoxLayout;
         mainLayout->addWidget(clientProgressBar);
         mainLayout->addWidget(clientStatusLabel);
         mainLayout->addWidget(serverProgressBar);
         mainLayout->addWidget(serverStatusLabel);
         mainLayout->addStretch(1);
         mainLayout->addSpacing(10);
         mainLayout->addWidget(buttonBox);
         setLayout(mainLayout);

         setWindowTitle(tr("Loopback"));
     }

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

     #ifndef QT_NO_CURSOR
         QApplication::setOverrideCursor(Qt::WaitCursor);
     #endif

         bytesWritten = 0;
         bytesReceived = 0;

         while (!tcpServer.isListening() && !tcpServer.listen()) {
             QMessageBox::StandardButton 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()
     {
         // called when the TCP client connected to the loopback server
         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);
     #ifndef QT_NO_CURSOR
             QApplication::restoreOverrideCursor();
     #endif
         }
     }

     void Dialog::updateClientProgress(qint64 numBytes)
     {
         // callen when the TCP client has written some bytes
         bytesWritten += (int)numBytes;

         // only write more if not finished and when the Qt write buffer is below a certain size.
         if (bytesToWrite > 0 && tcpClient.bytesToWrite() <= 4*PayloadSize)
             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);
     #ifndef QT_NO_CURSOR
         QApplication::restoreOverrideCursor();
     #endif
     }