server.cpp Example File

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 #include <QtWidgets>
 #include <QtNetwork>
 #include <QtCore>

 #include "server.h"

 Server::Server(QWidget *parent)
     : QDialog(parent)
     , statusLabel(new QLabel)
 {
     setWindowFlags(windowFlags() & ~Qt::WindowContextHelpButtonHint);
     statusLabel->setTextInteractionFlags(Qt::TextBrowserInteraction);

     QNetworkConfigurationManager manager;
     if (manager.capabilities() & QNetworkConfigurationManager::NetworkSessionRequired) {
         // Get saved network configuration
         QSettings settings(QSettings::UserScope, QLatin1String("QtProject"));
         settings.beginGroup(QLatin1String("QtNetwork"));
         const QString id = settings.value(QLatin1String("DefaultNetworkConfiguration")).toString();
         settings.endGroup();

         // If the saved network configuration is not currently discovered use the system default
         QNetworkConfiguration config = manager.configurationFromIdentifier(id);
         if ((config.state() & QNetworkConfiguration::Discovered) !=
             QNetworkConfiguration::Discovered) {
             config = manager.defaultConfiguration();
         }

         networkSession = new QNetworkSession(config, this);
         connect(networkSession, &QNetworkSession::opened, this, &Server::sessionOpened);

         statusLabel->setText(tr("Opening network session."));
         networkSession->open();
     } else {
         sessionOpened();
     }

     fortunes << tr("You've been leading a dog's life. Stay off the furniture.")
              << tr("You've got to think about tomorrow.")
              << tr("You will be surprised by a loud noise.")
              << tr("You will feel hungry again in another hour.")
              << tr("You might have mail.")
              << tr("You cannot kill time without injuring eternity.")
              << tr("Computers are not intelligent. They only think they are.");
     auto quitButton = new QPushButton(tr("Quit"));
     quitButton->setAutoDefault(false);
     connect(quitButton, &QAbstractButton::clicked, this, &QWidget::close);
     connect(tcpServer, &QTcpServer::newConnection, this, &Server::sendFortune);

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

     QVBoxLayout *mainLayout = nullptr;
     if (QGuiApplication::styleHints()->showIsFullScreen() || QGuiApplication::styleHints()->showIsMaximized()) {
         auto outerVerticalLayout = new QVBoxLayout(this);
         outerVerticalLayout->addItem(new QSpacerItem(0, 0, QSizePolicy::Ignored, QSizePolicy::MinimumExpanding));
         auto outerHorizontalLayout = new QHBoxLayout;
         outerHorizontalLayout->addItem(new QSpacerItem(0, 0, QSizePolicy::MinimumExpanding, QSizePolicy::Ignored));
         auto groupBox = new QGroupBox(QGuiApplication::applicationDisplayName());
         mainLayout = new QVBoxLayout(groupBox);
         outerHorizontalLayout->addWidget(groupBox);
         outerHorizontalLayout->addItem(new QSpacerItem(0, 0, QSizePolicy::MinimumExpanding, QSizePolicy::Ignored));
         outerVerticalLayout->addLayout(outerHorizontalLayout);
         outerVerticalLayout->addItem(new QSpacerItem(0, 0, QSizePolicy::Ignored, QSizePolicy::MinimumExpanding));
     } else {
         mainLayout = new QVBoxLayout(this);
     }

     mainLayout->addWidget(statusLabel);
     mainLayout->addLayout(buttonLayout);

     setWindowTitle(QGuiApplication::applicationDisplayName());
 }

 void Server::sessionOpened()
 {
     // Save the used configuration
     if (networkSession) {
         QNetworkConfiguration config = networkSession->configuration();
         QString id;
         if (config.type() == QNetworkConfiguration::UserChoice)
             id = networkSession->sessionProperty(QLatin1String("UserChoiceConfiguration")).toString();
         else
             id = config.identifier();

         QSettings settings(QSettings::UserScope, QLatin1String("QtProject"));
         settings.beginGroup(QLatin1String("QtNetwork"));
         settings.setValue(QLatin1String("DefaultNetworkConfiguration"), id);
         settings.endGroup();
     }

     tcpServer = new QTcpServer(this);
     if (!tcpServer->listen()) {
         QMessageBox::critical(this, tr("Fortune Server"),
                               tr("Unable to start the server: %1.")
                               .arg(tcpServer->errorString()));
         close();
         return;
     }
     QString ipAddress;
     QList<QHostAddress> ipAddressesList = QNetworkInterface::allAddresses();
     // use the first non-localhost IPv4 address
     for (int i = 0; i < ipAddressesList.size(); ++i) {
         if (ipAddressesList.at(i) != QHostAddress::LocalHost &&
             ipAddressesList.at(i).toIPv4Address()) {
             ipAddress = ipAddressesList.at(i).toString();
             break;
         }
     }
     // if we did not find one, use IPv4 localhost
     if (ipAddress.isEmpty())
         ipAddress = QHostAddress(QHostAddress::LocalHost).toString();
     statusLabel->setText(tr("The server is running on\n\nIP: %1\nport: %2\n\n"
                             "Run the Fortune Client example now.")
                          .arg(ipAddress).arg(tcpServer->serverPort()));
 }

 void Server::sendFortune()
 {
     QByteArray block;
     QDataStream out(&block, QIODevice::WriteOnly);
     out.setVersion(QDataStream::Qt_5_10);

     out << fortunes[QRandomGenerator::global()->bounded(fortunes.size())];

     QTcpSocket *clientConnection = tcpServer->nextPendingConnection();
     connect(clientConnection, &QAbstractSocket::disconnected,
             clientConnection, &QObject::deleteLater);

     clientConnection->write(block);
     clientConnection->disconnectFromHost();
 }