How to convert Object to byte [] and the inverse?

I need to upload a file over a udp connection to a college job. I created a package class that contains the header and part of the file to be submitted. I made the following method to convert the object to byte []:

 public static byte[] objectToByte(Object obj) throws IOException {
    ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
    ObjectOutputStream objectOutputStream = new ObjectOutputStream(byteArrayOutputStream);
    objectOutputStream.writeObject(obj);
    objectOutputStream.flush();
    objectOutputStream.close();
    byteArrayOutputStream.close();
    return byteArrayOutputStream.toByteArray();

}

And I created the following to convert back to Object:

public static Object byteToObject(byte[] bytes) throws IOException, ClassNotFoundException {
    ByteArrayInputStream byteArrayInputStream = new ByteArrayInputStream(bytes);
    ObjectInputStream objectInputStream = new ObjectInputStream(byteArrayInputStream);
    Object object = objectInputStream.readObject();
    objectInputStream.close();
    return object;
}

I tried the methods without sending over the connection and they worked, but when I send it through the datagram and the conversion is done back to Object it gives the error: java.io.StreamCorruptedException: invalid type code: 00 Just in this line:

Object object = objectInputStream.readObject();

Does anyone know what it can be?

Client Class method that starts sending packets:

public void executa(String host, int porta, String arquivo) throws ClassNotFoundException {
    try {
        InetAddress addr = InetAddress.getByName(host);
        this.porta = porta;
        this.caminho = arquivo;
        this.host=host;           
        //Fazendo HandShake
        Pacote pct = new Pacote(nSeq,ack,(short)2);
        DatagramPacket envio = new DatagramPacket(Manipulador.objectToByte(pct), 12, addr, porta);
        client = new DatagramSocket();
        //primeira msg
        client.send(envio);

The first packet is sent and then the error occurs when it arrives at the server on the thread that receives the packets:

public void run() {
    for (DatagramPacket pkg : servidor.getPacotes()) {
        try {

            Pacote pct = (Pacote) Manipulador.converterParaObject(pkg.getData());
            int flag = pct.getFlag();

At the time of converting the bytes received into the Package object. I had put a println upon receipt of the response from the server that never runs, so I realized that the error happens on the first submission.