QTcpsocket fast write data problem

I wrote the simple Tcp client-server app.
I have a Packet class, look like:
First 4 byte are the data type, and other are Data (QString) as Bytearray.

I have 3 threads.
Server -> User Manager -> Socket Thread.
So, when i try this ( for test ) :

Code:

for(int i =  0; i < 5;i++){
         Packet * teszt1 = new Packet;
        teszt1->setType(12);
        teszt1->setData("Something data teszt1 packet")
 
        Packet * teszt2 = new Packet;
        teszt2->setType(21);
        teszt2->setData("Something data teszt2 packet")
 
QMetaObject::invokeMethod(usersocket,"writeData",Qt::QueuedConnection,Q_ARG(Packet*,teszt1));
 
QMetaObject::invokeMethod(usersocket,"writeData",Qt::QueuedConnection,Q_ARG(Packet*,teszt2));
}

The package arrive ,but the teszt2 packet's type equal to the teszt1. (The data is different.)

BUT!!! When i add new line to my writeData method: QThread::msleep(30); It's work!
Why???

My writeData method:

Code:

void socketThread::writeData(Packet * packet)
{
    if(Socket->state() == QAbstractSocket::ConnectedState)
    {
        qDebug() << "Type: " << packet->getType(); //
        qDebug() << "Data: " << packet->getStringData(); 
        QByteArray kuldendo;
        *packet >> kuldendo;
        QByteArray Packetsize= Packet::IntToArray(packet->sizeOfPacket());
        Socket->write(Packetsize); //Sizeof(Packet type + Packet data)
        Socket->write(kuldendo); //Packet type + Packet data
        Socket->waitForBytesWritten();
        QThread::msleep(30); // <- without not work.
    }
    delete packet;
}

The client-side output without QThread::msleep(30) show :

Code:

---------------------
Packet Type: 12
Packet Data: "Something data teszt1 packet"
---------------------
NEW MESSAGE FROM SERVER
---------------------
Packet Type: 12
Packet Data: "Something data teszt2 packet"
---------------------
NEW MESSAGE FROM SERVER
---------------------
Packet Type: 12
Packet Data: "Something data teszt1 packet"
---------------------
NEW MESSAGE FROM SERVER
---------------------
Packet Type: 12
Packet Data: "Something data teszt2 packet"
---------------------
NEW MESSAGE FROM SERVER
---------------------
Packet Type: 12
Packet Data: "Something data teszt1 packet"
---------------------
NEW MESSAGE FROM SERVER
---------------------
Packet Type: 12
Packet Data: "Something data teszt2 packet"
---------------------
NEW MESSAGE FROM SERVER
---------------------
Packet Type: 12
Packet Data: "Something data teszt1 packet"
---------------------
NEW MESSAGE FROM SERVER
---------------------
Packet Type: 12
Packet Data: "Something data teszt2 packet"
---------------------
NEW MESSAGE FROM SERVER
---------------------
Packet Type: 12
Packet Data: "Something data teszt1 packet"
---------------------
NEW MESSAGE FROM SERVER
---------------------
Packet Type: 12
Packet Data: "Something data teszt2 packet"

I use Qt 5.7 with Static mingw compiler.
(OS: Windows 10)