Not trigger readyRead in another device (same LAN) when send multicast

SilentWolf

1/ PC1:
#define MULTICAST_PORT 8888
#define MULTICAST_IP "224.255.255.1"
onJoinMulticast(MULTICAST_IP, MULTICAST_PORT)

UdpMulticastAc::UdpMulticastAc()
{
    QString hostName = QHostInfo::localHostName();
    QString ip = getLocalIp();
    qDebug() << "Host name: " << hostName << ", Host IP：" << ip;

    m_udpSocket = new QUdpSocket(this);     //Socket for communication
    //Multicast routing level, 1 means only in the same LAN
    //Multicast TTL: Time to live, it will be reduced by 1 every time a route is crossed. Multicast cannot cross most routes, so it is 1
    //The default value is 1, which means that the data packet can only be transmitted in the local subnet.
    m_udpSocket->setSocketOption(QAbstractSocket::MulticastTtlOption, 1);

    connect(m_udpSocket, SIGNAL(stateChanged(QAbstractSocket::SocketState)), this, SLOT(onSocketStateChange(QAbstractSocket::SocketState)));
    onSocketStateChange(m_udpSocket->state());
    connect(m_udpSocket, SIGNAL(readyRead()), this, SLOT(onSocketReadyRead()));
}

void UdpMulticastAc::onJoinMulticast(QString ip, quint16 port)
{
    qDebug() << "onJoinMulticast ip = " << ip << ", port = " << port;
    m_groupAddress = QHostAddress(ip);

    if (m_udpSocket->bind(QHostAddress::AnyIPv4, port, QUdpSocket::ShareAddress)) {  // bind port
        m_udpSocket->joinMulticastGroup(m_groupAddress);  // Join the multicast group

        qDebug() << "[user: " << getLocalIp() << "]  Join multicast (multicast address: " << ip << " port: " << QString::number(port) << ")successfully!!!";
    } else {
        qDebug() << "[user: " << getLocalIp() << "]  Join multicast (multicast address: " << ip << " port: " << QString::number(port) << ")failure!!!";
    }
}

void UdpMulticastAc::onSocketReadyRead()
{
    qDebug("onSocketReadyRead");
    while (m_udpSocket->hasPendingDatagrams()) {
        QByteArray datagram;
        datagram.resize(m_udpSocket->pendingDatagramSize());

        QHostAddress peerAddr;
        quint16 peerPort;

        m_udpSocket->readDatagram(datagram.data(), datagram.size(), &peerAddr, &peerPort);  // Read data packet, message + Ip and port from
        QString str = datagram.data();
        QString peer = QString("[From: %1  %2] %3").arg(peerAddr.toString()).arg(QString::number(peerPort)).arg(str);
        qDebug() << peer;
}

2/ PC2: send message to group address

//Unicast message
void ExTrans::on_btnUnicast_clicked()
{
    QString targetIp = ui->comboBoxIp->currentText();
    QHostAddress targetAddr(targetIp);    // Target Ip
    quint16 targetPort = ui->spinBoxPort->value();   // Target port
    QString msg = ui->lineEdit->text();   // Message sent

    QByteArray str = msg.toUtf8();
    m_udpSocket->writeDatagram(str, targetAddr, targetPort);  // Send datagram

    ui->plainTextEdit->appendPlainText(QString("[Send: ] %1").arg(msg));
    ui->lineEdit->clear();
    ui->lineEdit->setFocus();
}

I tried this code in same PC, different applications: OK
But NOT OK wit different PCs

SGaist

Hi,

Here is solved thread with an issue similar as yours.

SilentWolf

@SGaist
I change value of group address but same
In another device (Jetson nano), i can join successfully but cannot receive data

![alt text](image url)

SGaist

Did you check the multicast sender example and its friend the multicast receiver example ?

SilentWolf

@SGaist yes, maybe only different with group port
45454 and 8888
How to find proper group port and IP in this case? I'm using 239.255.255.255.250:8888

I change port to 45454 but same issue

SilentWolf

@SGaist I found solution for it.
I use share network from my PC to jetson nano device so it make different subset: 10.42.0.* and 192.168.1.*
After plug both PC and jetson nano with same router, it worked
Thanks for your support