read() and readAll() return 0 bytes on readyRead() for multicast QUdpSocket

#include <QCoreApplication>

// add necessary includes here
#include <QUdpSocket>
#include <QDebug>
#include <QNetworkInterface>

int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);
    QUdpSocket * udpSocket = new QUdpSocket(&a);
    QObject::connect(udpSocket, &QUdpSocket::stateChanged, [=](){
        if (udpSocket->state() == QUdpSocket::BoundState) {
            if (!udpSocket->joinMulticastGroup(QHostAddress("232.1.1.12"))) {
                qDebug() << "Socket not bound to multicast group";
                return;
            }
            qDebug() << "Socket bound to multicast group";
            qDebug() << udpSocket->multicastInterface().hardwareAddress();
            qDebug() << udpSocket->multicastInterface().allAddresses();
            qDebug() << udpSocket->localAddress() << ":" << udpSocket->localPort();
            udpSocket->open(QAbstractSocket::ReadOnly);
            qDebug() << "isOpen = " << udpSocket->isOpen();
        }
    });
    QObject::connect(udpSocket, &QUdpSocket::readyRead, [=]() {
       qDebug() << "udpSocket" << udpSocket->bytesAvailable();
       qDebug() << "udpSocket" << udpSocket->hasPendingDatagrams();
       qDebug() << "udpSocket" << udpSocket->pendingDatagramSize();
       qDebug() << "udpSocket" << udpSocket->state();
       qDebug() << "udpSocket" << udpSocket->readAll().toHex();
    });

    QObject::connect(udpSocket, static_cast<void (QUdpSocket::*)(QUdpSocket::SocketError)>(&QUdpSocket::error), [=]() {
       qDebug() << udpSocket->errorString();
    });

//    udpSocket->bind(QHostAddress("10.10.3.103"), 21112, QUdpSocket::ShareAddress);
    udpSocket->bind(QHostAddress::AnyIPv4, 21112, QUdpSocket::ShareAddress);
//    udpSocket->connectToHost(QHostAddress("232.1.1.12"), 21112, QAbstractSocket::ReadOnly);
    return a.exec();
}

echo -ne "\xf0\x00\x04\x80\x01\x01" | socat - udp-datagram:232.1.1.12:21112,ip-add-membership=232.1.1.12:10.10.3.103