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how to send a datagram to the 239.255.255.250



  • I modfied the multicast sender example code to send a datagram to 239.255.255.250.
    On the Ubuntu 18.04 It works well,I also got the datagram by wireshark.
    On the windows the code is same with ubuntu,but it work failed .I can not got the datagram by wireshark. what is the problem?

    the code:

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    #include "sender.h"
    
    Sender::Sender(QWidget *parent)
        : QDialog(parent),
          groupAddress4(QStringLiteral("239.255.255.250")),
          groupAddress6(QStringLiteral("ff12::2115"))
    {
        // force binding to their respective families
    //    qDebug()<<udpSocket4.bind(QHostAddress(QHostAddress::AnyIPv4), 0);
        udpSocket4.bind(QHostAddress::AnyIPv4,1900,QUdpSocket::ShareAddress);
    
        udpSocket6.bind(QHostAddress(QHostAddress::AnyIPv6), udpSocket4.localPort());
    
        QString msg = tr("Ready to multicast datagrams to groups %1 and [%2] on port 20000").arg(groupAddress4.toString());
        if (udpSocket6.state() != QAbstractSocket::BoundState)
            msg = tr("IPv6 failed. Ready to multicast datagrams to group %1 on port 20000").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);
        qDebug()<<udpSocket4.writeDatagram(datagram, groupAddress4, 1900);
        if (udpSocket6.state() == QAbstractSocket::BoundState)
            udpSocket6.writeDatagram(datagram, groupAddress6, 1900);
        ++messageNo;
    }
    
    //your code here
    


  • @koahnig I solove the problem. the reason is the firewall is on,in addition to disabel the VMware 's network cad . thank you



  • @spite

    Did you check your firewalls and AV application for blocking the application?



  • This post is deleted!


  • @koahnig I solove the problem. the reason is the firewall is on,in addition to disabel the VMware 's network cad . thank you


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