sender.cpp Example File

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 #include <QtWidgets>
 #include <QtNetwork>

 #include "sender.h"

 Sender::Sender(QWidget *parent)
     : QDialog(parent)
 {
     groupAddress = QHostAddress("239.255.43.21");

     statusLabel = new QLabel(tr("Ready to multicast datagrams to group %1 on port 45454").arg(groupAddress.toString()));

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

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

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

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

     timer = new QTimer(this);
     udpSocket = new QUdpSocket(this);
     messageNo = 1;

     connect(ttlSpinBox, SIGNAL(valueChanged(int)), this, SLOT(ttlChanged(int)));
     connect(startButton, SIGNAL(clicked()), this, SLOT(startSending()));
     connect(quitButton, SIGNAL(clicked()), this, SLOT(close()));
     connect(timer, SIGNAL(timeout()), this, SLOT(sendDatagram()));

     QVBoxLayout *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)
 {
     udpSocket->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);
     udpSocket->writeDatagram(datagram.data(), datagram.size(),
                              groupAddress, 45454);
     ++messageNo;
 }