Server and multiple sockets

I'm a student, trying to write a server that can handle multiple
clients. It's closer to working than I was expecting but if I use
client 1, then client 2, client 1 then freezes. And then I can't close
the windows and have to stop the OS processes. The problem occurs with
this statement after port is defined:

      ServerSocket ss = new ServerSocket(port);

which causes this message:

     java.net.BindException: Address already in use: JVM_Bind

At that point no clients are running and nothing else has happened
with ports. I actually don't understand why the clients work at all,
since the socket doesn't seem to have been created successfully. After
the message above (and a trace), no other system messages appear
unless I try to close a window.

The following code includes comments using caps and ***, showing where
the trouble occurs. Any help greatly appreciated.

Chris
________________________________

package com.abc.server;

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import java.net.*;
import java.io.*;

public class Server extends JPanel implements Runnable {
    private static JTextArea serverLog;
    private static int port;
    private static Socket soc;
    private static ObjectOutputStream oos;
    private static ObjectInputStream ois;
    private Thread internalThread;
    private static PrintStream out;

    public static void main(String[] args) {
        JFrame f = new JFrame("Server");
        f.setSize(600, 350);
        f.setDefaultCloseOperation(f.EXIT_ON_CLOSE);
        f.setVisible(true);
        serverLog = new JTextArea();
        f.add(serverLog);

        out = new PrintStream(new TextAreaOutputStream(serverLog));
        System.setOut(out);
        System.setErr(out);

        f.addWindowListener(new WindowAdapter() {
            public void windowClosing(WindowEvent e) {
                try {
                    ois.close();
                    oos.flush();
                    oos.close();
                    soc.close();
                } catch ( IOException ioe ) {
                    System.out.println(ioe + "\n");
                    ioe.printStackTrace();
                }
                System.exit(0);
            }
        });
        port = 2001;
        Server server = new Server();
        System.out.println("Leaving main.");
    }

    public Server() {
        internalThread = new Thread(this);
        internalThread.start();
    }

    public void run() {
        System.out.println("Server ready.");

            int i = 1;
            System.out.println("Start of ");
            try {
            System.out.println("Start of connecting section. i = " +
i);
// *** EXECUTES CORRECTLY TO HERE
                ServerSocket ss = new ServerSocket(port);
// *** MESSAGE ISSUED HERE BUT SOCKET PARTIALLY WORKS
                for ( ;; ) {
                    Socket sock = ss.accept();
                    System.out.println("Got connection #" + i);
                    ClientService cs = new ClientService(sock, i,
out);
                    i++ ;
                }
            } catch ( IOException ioe ) {
                System.out.println(ioe + "\n");
                ioe.printStackTrace();
            }
// *** FOLLOWING PRINTS CORRECTLY BUT NO OTHER MESSAGES
        System.out.println("Connection established.");
    }
}

class ClientService implements Runnable {
    private static ObjectOutputStream oos;
    private static ObjectInputStream ois;
    private Thread internalThread;
    private Socket soc;
    private int counter;

    public ClientService(Socket s, int ctr, PrintStream outTxtArea) {
        soc = s;
        counter = ctr;
        PrintStream out = outTxtArea;
        System.setOut(out);
        System.setErr(out);
        internalThread = new Thread(this);
        internalThread.start();
        internalThread.interrupt();
    }

    public void run() {
        System.out.println("Thread for client #" + counter);
        try {
            final InputStream is = soc.getInputStream();
            oos = new ObjectOutputStream(soc.getOutputStream());
            ois = new ObjectInputStream(is);
            boolean done = false;
            while ( !done ) {
                String strFrmClnt = (String) ois.readObject();
                String strToClnt = strFrmClnt.length() + " - " +
strFrmClnt;
                if ( strFrmClnt == null ) {
                    done = true;
                } else {
                    oos.writeObject(strToClnt);
                }
            }
            ois.close();
            oos.flush();
            oos.close();
            soc.close();
        } catch ( ClassNotFoundException cnfe ) {
            System.out.println(cnfe + "\n");
            cnfe.printStackTrace();
        } catch ( IOException ioe ) {
            System.out.println(ioe + "\n");
            ioe.printStackTrace();
        }
    }
}