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();
       }
   }
}