java.io.StreamCorruptedException: invalid type code: 00

Question

So basically im writing a client-server multiplayer game. I have a SeverCommunicationThread that creates a gameThread if he receives a RequestForGame creates a gameThread. When i send a RequestForGame exception is thrown java.io.StreamCorruptedException: invalid type code: 00 I assume it's because both threads try to read the same ObjectInputStream, I don't have much understanding about how it works, i just know how to use it. Could you help me understand what's the problem and how to fix it? Thanks :)

public class ServerCommunicationThread extends Thread{
private Socket connectionSocket;
private ObjectInputStream inFromClient;
private ObjectOutputStream outToClient;
private String nickname;
private ServerModelManager model;


public ServerCommunicationThread(Socket connectionSocket,
        ServerModelManager model) throws IOException {
    this.connectionSocket = connectionSocket;
    inFromClient = new ObjectInputStream(connectionSocket.getInputStream());
    outToClient = new ObjectOutputStream(connectionSocket.getOutputStream());
    this.model = model;
    start();

}

public void run() {
    try {
        String nickname = (String) inFromClient.readObject();
        if (model.exists(nickname)){
            System.out.println(nickname + " already exists");
            outToClient.writeObject(new MessageForClient("Please choose another nickname"));
        }
        else
        {
            System.out.println(nickname + " connected, adding to list");
            model.addClient(nickname, connectionSocket,outToClient,inFromClient);
            this.nickname=nickname;
        }
        while(true){
            Object o= inFromClient.readObject();//StreamCorruptedexception
            if(o instanceof RequestForGame)
            {
                RequestForGame r=(RequestForGame)o;
                String userToPlayWith=r.getUserToPlayWith();
                if(userToPlayWith.equals(nickname))
                {
                    String message="Playing with yourself makes your palms hairy, choose another opponent";
                    outToClient.writeObject(message);
                }
                else
                {
                System.out.println("received request to play with "+userToPlayWith+". starting game");
                ClientRepresentative client1=model.getClient(nickname);
                ClientRepresentative client2=model.getClient(userToPlayWith);
                ServerGameThread s=new ServerGameThread(client2,client1,client2.getInStream(),client1.getInStream(),client1.getOutStream(),client2.getOutStream());
                }
            }
            else if(o instanceof String)
            {
                String s=(String) o;
                if(s.equals("i want to quit"))
                {
                    model.deleteClient(nickname);
                    inFromClient.close();
                    String q="quit";
                    outToClient.writeObject(q);
                    connectionSocket.close();
                    System.out.println(nickname+"has quit without exc");
                }
            }
        }
    } catch (EOFException e) {
        System.out.println(nickname+" has quit");
    }
    catch (SocketException e)
    {
        System.out.println(nickname+" has quit");
    }

    catch (Exception e) {

        e.printStackTrace();
    }
}

}
 public class ServerGameThread extends Thread {

private ClientRepresentative client1,client2;
private ObjectInputStream inFromClient1,inFromClient2;
private ObjectOutputStream outToClient1,outToClient2;
private Field gameField; 
public ServerGameThread(ClientRepresentative client1, ClientRepresentative client2,ObjectInputStream inFromClient1,ObjectInputStream inFromClient2,ObjectOutputStream outToClient1,ObjectOutputStream outToClient2)
{
    System.out.println("startin game thred");
    this.client1=client1;//client 1 goes first
    this.client2=client2;//client 2 started game


        this.inFromClient1=inFromClient1;
        this.inFromClient2=inFromClient2;
        this.outToClient1=outToClient1;
        this.outToClient2=outToClient2;


        gameField=new Field();
        System.out.println("check");
        start();
}
public void run()
{
    System.out.println("Starting game. players: "+client1.getNickname()+";"+client2.getNickname());
    try {
        outToClient1.writeObject(gameField);
        outToClient2.writeObject(gameField);
        while(true)
        {
            try {
                System.out.println("listening to "+client1.getNickname());
                Object o1=inFromClient1.readObject();//read move from client 1.**//StreamCorruptedexception**

                while(!(o1 instanceof PlayerMove))
                {
                    o1=inFromClient1.readObject();//read move from client 1.
                }
                PlayerMove move1=(PlayerMove)o1;
                System.out.println("received move "+move1+" sending to "+client2.getNickname());
                outToClient2.writeObject(move1);
                System.out.println("listening to "+client2.getNickname());
                Object o2=inFromClient2.readObject();//read move from client 1.
                while(!(o2 instanceof PlayerMove))
                {   
                    o2=inFromClient2.readObject();//read move from client 1.
                }
                PlayerMove move2=(PlayerMove)o2;
                System.out.println("received move "+move2+" sending to "+client1.getNickname());
                outToClient1.writeObject(move2);
            }
                catch (ClassNotFoundException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }

}
}    

the model.addClient method though i don't think the problem is here

  public void addClient(String nickname, Socket       clientSocket,ObjectOutputStream stream,ObjectInputStream inStream)
{
    clients.addClient(nickname, clientSocket,stream,inStream);//add to arraylist
//send client list to all clients
    String[] users=this.getAvailableClients();
    ObjectOutputStream[] streams=clients.getOutStreams();
    for(int i=0;i<streams.length;i++)
    {
        try {
            streams[i].writeObject(users);
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
}

The client side proxy that sends objects to server, the methods are triggered by user actions in GUI

  public class Proxy {
final int PORT = 1337;
String host;
String nickname;
private Socket clientSocket;
private ObjectOutputStream outToServer;
private ObjectInputStream inFromServer;
private ClientModelManager manager;
public Proxy(String nickname,String host,ClientModelManager manager)
{
    this.nickname=nickname;
    this.host=host;
    this.manager=manager;
    this.connect(nickname);
}
public void connect(String nick)
{
    Socket clientSocket;
    try {
        clientSocket = new Socket(host, PORT);
        System.out.println("client socket created");
        outToServer = new ObjectOutputStream(clientSocket.getOutputStream());
        inFromServer=new ObjectInputStream(clientSocket.getInputStream());
        outToServer.flush();
        outToServer.writeObject(nick);
        ClientReceiverThread t=new ClientReceiverThread(inFromServer,manager);
        t.start();
    } catch (Exception e) {
        e.printStackTrace();
    } 
}
public void makeRequest(String user)
{
    try
    {
    outToServer.writeObject(new RequestForGame(user));
    }
    catch(IOException e)
    {
        e.printStackTrace();
    }
}
public void quit()
{
    try {
        outToServer.writeObject(new String("i want to quit"));
        //clientSocket.close();
    } catch (IOException e) {
        e.printStackTrace();
    }
}
public void sendMove(PlayerMove move)
{
    try {
        outToServer.writeObject(move);
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
}

}

Answer 1

This problem can happen if you

• construct a new ObjectInputStream or ObjectOutputStream over the same socket instead of using the same ones for the life of the socket;
• use another kind of stream over the same socket as well; or,
• use the object streams to read or write something that isn't an object and you get out of sync.