Qt 5.6 | Qt Network | Loopback Example | dialog.cpp Example File

Qt 5.6.3 Reference Documentation

# dialog.cpp Example File

loopback/dialog.cpp

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      ** This file is part of the examples of the Qt Toolkit.
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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
      }