dialog.cpp Example File

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  #include <QtWidgets>
  #include <QtNetwork>

  #include "dialog.h"

  static const int TotalBytes = 50 * 1024 * 1024;
  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
  }