Java exception when I want to send object using socket

Question

i want to make server client application, where server will waiting for object and when server get the object then make someting with it. But I have problem when server want to get the object.

Server:

public static void main(String[] argv) throws IOException {
    String command;
    List<Game> games = new ArrayList<>();
    List<Player> players = new ArrayList<>();

    serverSocket = new ServerSocket(9999);

    while(true){
        System.out.println("Waiting for player");
        Socket socket = serverSocket.accept();
        System.out.println("Player connected, waiting for command");

        ObjectOutputStream out = new ObjectOutputStream(socket.getOutputStream());
        System.out.println("Output created");

        Player p = new Player(out);
        players.add(p);
        ObjectInputStream in = new ObjectInputStream(socket.getInputStream());
        System.out.println("input created");
        ServerReceiver receiver = new ServerReceiver(games, players, in);
        receiver.start();

    }
}

public class ServerReceiver extends Thread{

private List<Game> games;
private List<Player> players;
private ObjectInputStream in;

public ServerReceiver(List<Game> games, List<Player> players, ObjectInputStream in) throws IOException{
    this.games = games;
    this.players = players;
    this.in = in;
}

@Override
public void run(){
    CommandMessage message = null;
    System.out.println("in thread");
    while(true){
        try {
            message = (CommandMessage) in.readObject();

        } catch (IOException ex) {
            Logger.getLogger(ServerReceiver.class.getName()).log(Level.SEVERE, null, ex);
        } catch (ClassNotFoundException ex) {
            Logger.getLogger(ServerReceiver.class.getName()).log(Level.SEVERE, null, ex);
        }

    }
}

}

Client:

public static void main(String[] argv) throws IOException, ClassNotFoundException{
    socket = new Socket("localhost",9999);
    System.out.println("Connected");

    in = new ObjectInputStream(socket.getInputStream());
    Integer id = (Integer) in.readObject();
    System.out.println(id);
    out = new ObjectOutputStream(socket.getOutputStream());
    out.flush();

    CommandMessage m = new CommandMessage(0, 0, null);
    m.setName("Name");
    out.writeObject(m);

}

and server output:

Waiting for player
Player connected, waiting for command
Output created
input created
Waiting for player
in thread
III 16, 2014 12:24:20 DOP. Comunication.ServerReceiver run
SEVERE: null
java.io.WriteAbortedException: writing aborted; java.io.NotSerializableException:   Comunication.CommandMessage
at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1354)
at java.io.ObjectInputStream.readObject(ObjectInputStream.java:370)
at Comunication.ServerReceiver.run(ServerReceiver.java:40)
Caused by: java.io.NotSerializableException: Comunication.CommandMessage
at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1183)
at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:347)
at Client.main(Client.java:37)

Client output:

Connected
0
Exception in thread "main" java.io.NotSerializableException: Comunication.CommandMessage
at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1183)
at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:347)
at Client.main(Client.java:37)
Java Result: 1

What can I do wrong? or can somebody tell me how to do it better if my idea is not good?

Answer 1

You read an object in loop, but when client disconect you must somehow handle exception and do not read other object from ObjectInputStream

Answer 2

The error message is perfectly clear. Your CommandMessage class doesn't implement Serializable. Fix that.

Answer 3

Objects that you want to serialize, what you are doing while sending it over the network have to implement Serializeable: http://docs.oracle.com/javase/7/docs/api/java/io/Serializable.html