Unsolved custom modbus function code

[Lapsi]

I need to add a custom Modbus function code in Qt. It doesn't have any parameters and as a result I expect to get a constant data-length packet.

int main(int argc, char *argv[])
{
QApplication a(argc, argv);
QObject *connector = new QObject();

QModbusTcpClient *client = new QModbusTcpClient();
client->setConnectionParameter(QModbusDevice::NetworkAddressParameter, "127.0.0.1");
client->setConnectionParameter(QModbusDevice::NetworkPortParameter, 8899);
client->connectDevice();
connector->connect(client, &QModbusClient::stateChanged, connector, [connector, client]()
{
    if(client->state() == QModbusClient::ConnectedState)
    {
        auto cmd = QModbusPdu::FunctionCode(0x66);
        QModbusRequest request(cmd);
        QModbusReply* reply = client->sendRawRequest(request, 1);

        connector->connect(reply, &QModbusReply::finished, connector, [reply]()
        {
            qInfo() << "isFinished? " << reply->isFinished(); // true
            qInfo() << "Raw result fun code: " << reply->rawResult().functionCode(); // 0
            qInfo() << "Error? " << reply->errorString(); //""
            qInfo() << "Reply data size: " << reply->rawResult().dataSize(); // 0
            qInfo() << "Reply size: " << reply->rawResult().data().size(); // 0
            QByteArray data = reply->rawResult().data(); // empty
        });
    }
});

return a.exec();

}

The other side receives the packet correctly and sends the answer back. The sent answer looks like this:

0x0000, 0x0000, 0x0007, // Modbus TCP header
0x01, 0x66, // general Modbus header
0x04, // the response size is 4 bytes
0x0000, 0x0042 // 4 bytes of response

But nothing is received in Qt (the reply finishes but there is nothing in it)

I've tried this solution - https://bugreports.qt.io/browse/QTBUG-62192 but it doesn't work.