Overcoming this runtime exception

Hi All,

I have JB9 personal and win2k.

It is my belief that in order to make this server  program run I need the server to be up and running before I open a client or the associated applet .  

Yet  this chat server demo  refuses to run because of this error as reported

     java.lang.RuntimeException: Syntax: ChatServer <port>

      at objectschatserver.ChatServer.main(ChatServer.java:20)

Exception in thread "main"        

There are  two classes that comprise the :

package objectschatserver;

import java.net.*;
import java.io.*;
import java.util.*;

public class ChatServer {
  public ChatServer (int port) throws IOException {
    ServerSocket server = new ServerSocket (port);
    while (true) {
      Socket client = server.accept ();
      System.out.println ("Accepted from " + client.getInetAddress ());
      ChatHandler c = new ChatHandler (client);
      c.start ();

  public static void main (String args[]) throws IOException {
    if (args.length != 1)
      throw new RuntimeException ("Syntax: ChatServer <port>");
    new ChatServer (Integer.parseInt (args[0]));

package objectschatserver;

import java.net.*;
import java.io.*;
import java.util.*;

public class ChatHandler extends Thread {
  protected Socket s;
  protected DataInputStream i;
  protected DataOutputStream o;

  public ChatHandler (Socket s) throws IOException {
    this.s = s;
    i = new DataInputStream (new BufferedInputStream (s.getInputStream ()));
    o = new DataOutputStream (new BufferedOutputStream (s.getOutputStream ()));

  protected static Vector handlers = new Vector ();

  public void run () {
    String name = s.getInetAddress ().toString ();
    try {
      broadcast (name + " has joined.");
      handlers.addElement (this);
      while (true) {
        String msg = i.readUTF ();
        broadcast (name + " - " + msg);
    } catch (IOException ex) {
      ex.printStackTrace ();
    } finally {
      handlers.removeElement (this);
      broadcast (name + " has left.");
      try {
        s.close ();
      } catch (IOException ex) {

  protected static void broadcast (String message) {
    synchronized (handlers) {
      Enumeration e = handlers.elements ();
      while (e.hasMoreElements ()) {
        ChatHandler c = (ChatHandler) e.nextElement ();
        try {
          synchronized (c.o) {
            c.o.writeUTF (message);
          c.o.flush ();
        } catch (IOException ex) {
          c.stop ();

What is it needing or can that error be compromised with something else to make it run.

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Call it like:

java ChatServer 2222

to open it on port 2222
or, change the main method in ChatServer to be:

public static void main (String args[]) throws IOException
    int port = 2222 ;

    if( args.length > 0 )
          port = Integer.parseInt( args[ 0 ] ) ;

    new ChatServer( port );

then it will default to 2222, unless you pass a different port number to listen on

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There no need to throw an exception if args.length > 1 so it should be

    if (args.length < 1)
      throw new RuntimeException ("Syntax: ChatServer <port>");

Make sure you pass the port number
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if you are running the chatserver inside JB9, then you need to alter the "Run->Configuration", and add 2222 as application parameters :-)
Mick BarryJava DeveloperCommented:
> There no need to throw an exception if args.length > 1 so it should be

But doesn't hurt, and it is invalid syntax.

> Make sure you pass the port number

already well covered.

delphi3Author Commented:
Thanks to you all,

Tim you're the greatest.

However, I am still frustrated now that this matter above has been taken care of.   Just now  there are
further problems with this super sample example of the chat that I am working with.

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