Java: how to detect in the server, whether a client socket has been closed?

Question

Environment: Java 6, windows xp

I am trying to write a client-server TCP socket application. Need to detect on the server, when the client has closed the socket. All the information on the Internet, says that the server will throw a socket exception when its not able to write.

However, when I run the code (see below), I see that the server gets the exception only when the client doesn't read anything from the stream. When the client reads from the input stream, no exception is thrown on the server.

can someone please tell me the right way to detect a client side socket close (and also explain the behavior exhibited by the code below)?

Code:

package com.connection;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.Writer;
import java.net.ServerSocket;
import java.net.Socket;

public class Test implements Runnable{
    ServerSocket ss = null;
    public Test() throws Exception{
        ss = new ServerSocket(9999);
    }
    public void run(){
        try{
        Socket s = ss.accept();
        Writer w = new OutputStreamWriter(s.getOutputStream());
        w.write("Hello\n");
        w.flush();
        System.out.println("Server: wrote string 1");
        System.out.println("Server: sleeping...");
        Thread.sleep(5000);
        System.out.println("Server: woke up");
        w.write("Hello\n");
        w.flush();
        System.out.println("Server: wrote string 2");
        }catch(Exception e) {
            e.printStackTrace();
        }
    }
    public static void main(String[] args) throws Exception{
        Thread server = new Thread(new Test());
        server.start();
        Thread client = new Thread(new TestClient());
        client.start();
    }
}
class TestClient implements Runnable{

    public void run() {
        try {
            Socket s = new Socket("localhost", 9999);
            // Comment out the below 4 lines to see the write exception on server
            BufferedReader r = new BufferedReader(new InputStreamReader(s.getInputStream()));
            System.out.println("Client: reading input...");
            String str = r.readLine();
            System.out.println(str);
            // Comment the *above* 4 lines to see exception on server
            Thread.sleep(1000);
            System.out.println("Client: woke up");
            s.close();
            System.out.println("Client: socket closed");
        }catch(Exception e){
            e.printStackTrace();
        }
    }
}