sender.cpp Example File

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 #include "sender.h"

 Sender::Sender(QWidget *parent)
     : QDialog(parent),
       groupAddress4(QStringLiteral("239.255.43.21")),
       groupAddress6(QStringLiteral("ff12::2115"))
 {
     // force binding to their respective families
     udpSocket4.bind(QHostAddress(QHostAddress::AnyIPv4), 0);
     udpSocket6.bind(QHostAddress(QHostAddress::AnyIPv6), udpSocket4.localPort());

     QString msg = tr("Ready to multicast datagrams to groups %1 and [%2] on port 45454").arg(groupAddress4.toString());
     if (udpSocket6.state() != QAbstractSocket::BoundState)
         msg = tr("IPv6 failed. Ready to multicast datagrams to group %1 on port 45454").arg(groupAddress4.toString());
     else
         msg = msg.arg(groupAddress6.toString());
     statusLabel = new QLabel(msg);

     auto ttlLabel = new QLabel(tr("TTL for IPv4 multicast datagrams:"));
     auto ttlSpinBox = new QSpinBox;
     ttlSpinBox->setRange(0, 255);

     auto ttlLayout = new QHBoxLayout;
     ttlLayout->addWidget(ttlLabel);
     ttlLayout->addWidget(ttlSpinBox);

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

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

     connect(ttlSpinBox, QOverload<int>::of(&QSpinBox::valueChanged), this, &Sender::ttlChanged);
     connect(startButton, &QPushButton::clicked, this, &Sender::startSending);
     connect(quitButton, &QPushButton::clicked, this, &Sender::close);
     connect(&timer, &QTimer::timeout, this, &Sender::sendDatagram);

     auto mainLayout = new QVBoxLayout;
     mainLayout->addWidget(statusLabel);
     mainLayout->addLayout(ttlLayout);
     mainLayout->addWidget(buttonBox);
     setLayout(mainLayout);

     setWindowTitle(tr("Multicast Sender"));
     ttlSpinBox->setValue(1);
 }

 void Sender::ttlChanged(int newTtl)
 {
     // we only set the TTL on the IPv4 socket, as that changes the multicast scope
     udpSocket4.setSocketOption(QAbstractSocket::MulticastTtlOption, newTtl);
 }

 void Sender::startSending()
 {
     startButton->setEnabled(false);
     timer.start(1000);
 }

 void Sender::sendDatagram()
 {
     statusLabel->setText(tr("Now sending datagram %1").arg(messageNo));
     QByteArray datagram = "Multicast message " + QByteArray::number(messageNo);
     udpSocket4.writeDatagram(datagram, groupAddress4, 45454);
     if (udpSocket6.state() == QAbstractSocket::BoundState)
         udpSocket6.writeDatagram(datagram, groupAddress6, 45454);
     ++messageNo;
 }