#/* author: Stan McCaslin (mccaslin@scis.acast.nova.edu) */
/* date: 16-Jul-1996                                    */
/* A simple java chat server.  Modeled after the echo server
   in Core Java by Cornell and Horstmann Sunsoft Press, 1996 p 561 */
import java.io.*;
import java.net.*;

class Chat
{
public static void main(String[] args)
	{
	int i = 1;
	int portval;
	LinkedList list = new LinkedList();
	try
		{
		if (args.length == 0)
			portval = 6001;
		else
			{
			Integer port = new Integer(args[0]);
			portval = port.intValue();
			}
		ServerSocket s = new ServerSocket(portval);
		for (;;)
			{
			Socket incoming = s.accept();
			System.out.println("Spawning " + i);
			new ThreadedChatHandler(incoming, i, list).start();
			i++;
			}
		}
		catch (Exception e)
		{ System.out.println(e);
		}
	}
}

class ThreadedChatHandler extends Thread
{ Socket incoming;
  int counter;
  LinkedList list;
  ThreadedChatHandler(Socket i, int c, LinkedList a)
	{incoming = i; counter=c; list = a;}
  public void run()
  { try
	{DataInputStream in = new DataInputStream(incoming.getInputStream());
	 PrintStream out = new PrintStream(incoming.getOutputStream());
	 list.append(out); 
	 out.println("Welcome! Enter BYE to exit.\r");
	 out.println("Please enter a short id for this session.\r");
	 String id = in.readLine();
	 printall("Just signed on\r", id, out);
	 boolean done = false;
	 while (!done)
	 { String str = in.readLine();
	   if (str == null) done = true;
	   else
		{
		printall(str + "\r", id, out);
		if (str.trim().equals("BYE"))
			done = true;
		}
  	  }
	  list.reset();
	  while (list.hasMoreElements())
		{
		if (out == (PrintStream)list.currentElement())	
			{
	  		list.remove();
			break;
			}
		}
	  in.close();
	  out.close();
	  incoming.close();
   }
   catch(Exception e)
	{System.out.println(e); }
   }
public synchronized void printall(String str, String id, PrintStream noecho)
   {
   PrintStream o;
   list.reset();
   while (list.hasMoreElements())
	{
        o = (PrintStream)list.currentElement();
        list.nextElement();
	/* if (o != noecho) */
        	o.println(id + ": " + str);
	}
   }	
}

	
	
/*
 * Gary Cornell and Cay S. Horstmann, Core Java (Book/CD-ROM)
 * Published By SunSoft Press/Prentice-Hall
 * Copyright (C) 1996 Sun Microsystems Inc.
 * All Rights Reserved. ISBN 0-13-565755-5
 *
 * Permission to use, copy, modify, and distribute this 
 * software and its documentation for NON-COMMERCIAL purposes
 * and without fee is hereby granted provided that this 
 * copyright notice appears in all copies. 
 * 
 * THE AUTHORS AND PUBLISHER MAKE NO REPRESENTATIONS OR 
 * WARRANTIES ABOUT THE SUITABILITY OF THE SOFTWARE, EITHER 
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE 
 * IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A 
 * PARTICULAR PURPOSE, OR NON-INFRINGEMENT. THE AUTHORS
 * AND PUBLISHER SHALL NOT BE LIABLE FOR ANY DAMAGES SUFFERED 
 * BY LICENSEE AS A RESULT OF USING, MODIFYING OR DISTRIBUTING 
 * THIS SOFTWARE OR ITS DERIVATIVES.
 */
 
/**
 * A simple implementation of a linked list
 * @version 1.01 15 Feb 1996 
 * @author Cay Horstmann
 */

/* public class LinkedList */
class LinkedList
{  /** 
   * resets the cursor
   */
   
   public void reset()

   {  pre = null;
   }



   /**
    * @return true iff the cursor is not at the end of the
    * list 
    */
    public boolean hasMoreElements() 
   
   {  return cursor() != null;
   }


   /**
    * move the cursor to the next position
    * @return the current element (before advancing the 
    * position)
    * @exception java.util.NoSuchElementException if already at the
    * end of the list
    */
    public Object nextElement()
   
   {  if (pre == null) pre = head; else pre = pre.next;
      if (pre == null) 
         throw new java.util.NoSuchElementException();
      return pre.data;
   }


   /**
    * @return the current element under the cursor
    * @exception java.util.NoSuchElementException if already at the
    * end of the list
    */
   
   public Object currentElement() 
   
   {  Link cur = cursor();
      if (cur == null) 
         throw new java.util.NoSuchElementException();
      return cur.data;
   }

   /**
    * insert after the tail of the list
    * @param n - the value to insert
    */
   
   public void append(Object n)
   
   {  Link p = new Link(n, null);
      if (head == null) head = tail = p;
      else
      {  tail.next = p;
         tail = p;
      }
      len++;
   }


   /**
    * remove the element under the cursor
    * @return the removed element
    * @exception java.util.NoSuchElementException if already at the 
    * end of the list
    */
    public Object remove()
   
   {  Link cur = cursor();
      if (cur == null) 
         throw new java.util.NoSuchElementException();
      if (tail == cur) tail = pre;
      if (pre != null)
         pre.next = cur.next;
      else
         head = cur.next;
      len--;
      return cur.data;
   }

   private Link cursor() 
   {  if (pre == null) return head; else return pre.next;
   }
   
   private Link head;
   private Link tail;
   private Link pre; // predecessor of cursor
   private int len;
 
}

class Link
{  Object data;
   Link next;
   Link(Object d, Link n) { data = d; next = n; }
}