EOFException occured when send many objects over socket

Question

I am making a program that uses socket to connect to others. When I send String or array of String it works fine. But when I try to send Objects over socket it doesnt work and EOFException appeared. I tried to find out by my own but its seem too hard for me!

Here is the input function in the Client: (I have many case in this function but they work fine so just the case has the problem)

public void run()
{
while(true)
        {
            try 
            {
                int dataType = (int)in.readByte(); // this line is where the exception appeared. every works fine with another case
                switch(dataType)
                {
                case 2:
                        {
                            try 
                            {
                               int nRoom = (int)in.readByte(); // read the number of room are created

                                for (int i = 0; i < nRoom; i++)
                                {

                                    Server.Room temp = (Server.Room) in.readObject();
                                    nRooms[temp.ID] = temp;

                                }
                            } 
                            catch (ClassNotFoundException ex) 
                            {
                                System.out.println(ex.toString());
                            }
                        }

                    break;
                }  
            }
            catch (EOFException e)
            {

               System.out.println(e.toString());

            }
            catch (IOException ex) 
            {
                System.out.println(ex.toString());
                break;
            }
   }
}

Here is the outPut function in the Client:

private void createBtnClick( java.awt.event.ActionEvent evt )      
{
    try 
    {
        out.writeByte(2);
        out.flush();
    } 
    catch (IOException ex) 
    {
        System.out.println(ex.toString);
    }
}

Here is the function the server take the input then write output to every Client ( its the user in the code below ):

public void run()
    {
       while(true)
        {
            try 
            {

                int command = users[index].in.readByte();
                switch ( command)
                {
                        case 2:   
                        // create the room

                        for (int i = 0; i < 5; i++) 
                        {
                            if(nRooms[i] == null)
                            {
                                nRooms[i] = new Room(users[i].name,"Beginner", 1, i);
                                users[index].State = 1;
                                System.out.println("SV : create room  ok " + i);
                                break;
                            }
                        }
                        for (int i = 0; i < 10; i++) 
                        {
                            if(users[i] != null && i != index && ) // Send the room list to everybody except the room host!
                            {
                                try 
                                {
                                    users[i].out.writeByte(2);
                                    int count = 0;
                                    for (int j = 0; j < 5; j++) 
                                    {
                                        if(nRooms[j] != null)
                                            count++;
                                    }
                                    users[i].out.writeByte(count);
                                    for (int j = 0; j < 5; j++)
                                    {
                                        if(nRooms[j] != null);
                                        {
                                            users[i].out.writeObject( nRooms[j]);
                                           break;
                                        }


                                    }
                                     //users[i].out.flush();
                                } 
                                catch (IOException ex)
                                {
                                    System.out.println(ex.toString());
                                }

                            }
                        }
                        break;
                }
            } 

            catch (IOException ex) 
            {
                System.out.println(ex.toString());
                users[index].in = null;
                users[index].out = null;
                users[index] = null;
                break;
            }
        }

Room class is just a class that holds some infomation : (Define in Server)

public class Room implements Serializable
{
    public String hostName;
    public String gameMode;
    public int nPlayers;
    public int ID;
    public Room(String hostName, String gameMode, int nPlayers, int ID) 
    {
        this.hostName = hostName;
        this.gameMode = gameMode;
        this.nPlayers = nPlayers;
        this.ID = ID;
    }

}

Thanks!