struct uidType{
    uint16_t uid1 = 0;
    uint32_t uid2 = 0;
    uint16_t uid3 = 0;
    uint32_t uid4 = 0;
};

QByteArray errorByteArr;
    QDataStream out(&errorByteArr, QIODevice::WriteOnly | QIODevice::Append);
    out.setByteOrder(QDataStream::BigEndian);
    out << (quint8) STM32_PACK_TITLE;
    out << (quint8) STM32_PACK_SIZE;
    out << (quint16) 0x0000;
    out << (quint8) 0xFF;
    out << (quint16) errorCode;
...................
socketClient.write(errorByteArr,STM32_PACK_SIZE);