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A simple Chat program with Client/Server (GUI optional) Rate Topic: ***** 2 Votes

#16 josiahmahar  Icon User is offline

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Posted 18 January 2012 - 05:19 PM

hey i followed your tutorial the server and client work great when you open them through command prompt. however when i try to put it in jar files (one for the client and one for the server)it will say in the client that i have signed in but on the server the client doesn't connect and i cant send messages. do you know a way i could get this to work?
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#17 ob22  Icon User is offline

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Posted 18 January 2012 - 09:03 PM

yes finally it works thank for the reply.. now i want to distribute the load for the servers among different servers(normal computers) where clients will connect to a main server than redirect to the other small servers. But can we can me an idea of how to more how many clients are being connected to each different servers please.
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#18 LinuxIsNotAProcessor  Icon User is offline

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Posted 10 March 2012 - 09:05 PM

How do I get access to ClientThread? Is it from org.apache.commons.performance.ClientThread and if so how do I get access to it in my program?
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#19 LinuxIsNotAProcessor  Icon User is offline

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Posted 10 March 2012 - 09:11 PM

View PostLinuxIsNotAProcessor, on 10 March 2012 - 09:05 PM, said:

How do I get access to ClientThread? Is it from org.apache.commons.performance.ClientThread and if so how do I get access to it in my program?


Update: Please ignore, I need to learn to scroll down. :)
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#20 genti  Icon User is offline

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Posted 12 July 2012 - 01:18 PM

I tried to change the user name from Anonymous to another name from console,but it doesn't work.

>java Client Jack 1500 localhost

or

>java Client [Tom] [1500] [localhost]

where is the problem..
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#21 DxnadxC  Icon User is offline

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Posted 26 July 2012 - 01:12 AM

Hello, this is awesome. I wanted to if I could chat to my friends through this? If so would we all need an internet connection? Thanks in advance.
P.S. would it matter if they have mac or PC?
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#22 JackOfAllTrades  Icon User is offline

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Posted 26 July 2012 - 03:59 AM

View PostDxnadxC, on 26 July 2012 - 04:12 AM, said:

I wanted to if I could chat to my friends through this? If so would we all need an internet connection?


I think the upcoming version of the Java SDK has a Telepathy interface for the Scanner class, so keep an eye out for that.

On the other hand, if your friends are all on the same LAN, you could in fact do this.
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#23 Jumanjiarumugam  Icon User is offline

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Posted 30 July 2012 - 12:01 AM

Hi sir, this is a awesome tutorial!!
In this tutorial your server broadcasts whatever the client types in to all the other clients that are connected.
What should I do to let the client choose another client to chat instead of server broadcasting it to all clients that are connected
the server just have to send the message to one particular client.
Thank you!!!
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#24 piyushjain220  Icon User is offline

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Posted 06 August 2012 - 02:18 PM

Hi All,
I am a newbie, wanted to check how to run this code..
I installed eclipse and created a project and put all the 5 files in it.
But it gives few errors for Server.java
The constructor Server(int, ServerGUI) refers to the missing type ServerGUI Server.java /Chat/src line 29

and 1 warning for Client.java
Resource leak: 'scan' is never closed Client.java /Chat/src line 194

Can someone tell me what could be done to solve this or rather run this properly?
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#25 poison766  Icon User is offline

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Posted 16 August 2012 - 12:39 PM

Hello, can you say what it need to do that Client can speak with other Client private.
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#26 shashank.jayakrishna  Icon User is offline

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Posted 31 January 2013 - 07:23 AM

hi can u tell me how to use this app on two different PC's, I am getting an error unknown server exception when i tried to connect to server through another PC
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#27 AndrewTH  Icon User is offline

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Posted 24 February 2013 - 04:53 AM

Hi, thanks for this chatting program. It's very cool but I have one question, I want to make the client show all client's names those join in chat server. How can I do that ?

Thanks a lot ^^
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#28 oha055  Icon User is offline

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Posted 26 February 2013 - 08:45 AM

great tut!
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#29 supupoff  Icon User is offline

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Posted 28 February 2013 - 08:29 AM

thanks for topic it's very Helpfull,
i have a Question,
if i want to add this Project to my project how i do, cause i tried many ways but can't make it works
Thanks Again,
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#30 shahsaurabh85@gmail.com  Icon User is offline

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Posted 10 April 2013 - 12:32 AM

View Postpbl, on 13 December 2011 - 08:37 PM, said:

Many times in the forum we see questions about Chat programs which imply:
- TCP connections
- Threads
- and a GUI most of the times

So here is a very simple Chat program from which you can inspire yourself. The most important point is to give you code

examples to which we will be able to refer you when you will have a problem in your code.

The code contains 5 classes that you can cut & paste in a directory on your PC and it should work.
The 5 classes are:
- ChatMessage.java
- Server.java
- Client.java
- ServerGUI.java
- ClientGUI.java

Actually, if you want to run the application in console mode, you only need the first 3 classes. The two GUI classes can be used as a bonus, it is a very simple GUI. You can run both the Client and the Server in GUI mode or only one of the two in GUI mode.

The ChatMessage class.

When you establish connections over TCP it is only a serie of bytes that are actually sent over the wire. If you have a Java application that talks to a C++ application you need to send series of bytes and have both the sender and the receiver to agree on what these bytes represent.

When talking between two Java applications, if both have access to the same code, I personally prefer to send Java Object between the two applications. Actually it will still a stream of bytes that will be sent over the internet but Java will do the job of serializing and deserializing the Java objects for you. To do that you have to create an ObjectInputStream and an ObjectOutputStream from the Socket InputStream and the Socket OutputStream.

The objects sent of the sockets have to implements Serializable.
In this application, all the messages sent from the Server to the Client are String objects. All the messages sent from the Client to the Server (but the first one which is a String) are ChatMessage. ChatMessage have a type and a String that contains the actual message.

ChatMessage.java

import java.io.*;
/*
 * This class defines the different type of messages that will be exchanged between the
 * Clients and the Server. 
 * When talking from a Java Client to a Java Server a lot easier to pass Java objects, no 
 * need to count bytes or to wait for a line feed at the end of the frame
 */
public class ChatMessage implements Serializable {

	protected static final long serialVersionUID = 1112122200L;

	// The different types of message sent by the Client
	// WHOISIN to receive the list of the users connected
	// MESSAGE an ordinary message
	// LOGOUT to disconnect from the Server
	static final int WHOISIN = 0, MESSAGE = 1, LOGOUT = 2;
	private int type;
	private String message;
	
	// constructor
	ChatMessage(int type, String message) {
		this.type = type;
		this.message = message;
	}
	
	// getters
	int getType() {
		return type;
	}
	String getMessage() {
		return message;
	}
}



Now the Server class.

You can start the Server by typing
> java Server
at the console prompt. That will execute it in console mode and the server will wait for connection on port 1500. To use another port pass the port number to use as first parameter to the command
> java Server 1200
will ask the Server to listen on port 1200.
You can use <CTRL>C to stop the server.

Server.java
import java.io.*;
import java.net.*;
import java.text.SimpleDateFormat;
import java.util.*;

/*
 * The server that can be run both as a console application or a GUI
 */
public class Server {
	// a unique ID for each connection
	private static int uniqueId;
	// an ArrayList to keep the list of the Client
	private ArrayList<ClientThread> al;
	// if I am in a GUI
	private ServerGUI sg;
	// to display time
	private SimpleDateFormat sdf;
	// the port number to listen for connection
	private int port;
	// the boolean that will be turned of to stop the server
	private boolean keepGoing;
	

	/*
	 *  server constructor that receive the port to listen to for connection as parameter
	 *  in console
	 */
	public Server(int port) {
		this(port, null);
	}
	
	public Server(int port, ServerGUI sg) {
		// GUI or not
		this.sg = sg;
		// the port
		this.port = port;
		// to display hh:mm:ss
		sdf = new SimpleDateFormat("HH:mm:ss");
		// ArrayList for the Client list
		al = new ArrayList<ClientThread>();
	}
	
	public void start() {
		keepGoing = true;
		/* create socket server and wait for connection requests */
		try 
		{
			// the socket used by the server
			ServerSocket serverSocket = new ServerSocket(port);

			// infinite loop to wait for connections
			while(keepGoing) 
			{
				// format message saying we are waiting
				display("Server waiting for Clients on port " + port + ".");
				
				Socket socket = serverSocket.accept();  	// accept connection
				// if I was asked to stop
				if(!keepGoing)
					break;
				ClientThread t = new ClientThread(socket);  // make a thread of it
				al.add(t);									// save it in the ArrayList
				t.start();
			}
			// I was asked to stop
			try {
				serverSocket.close();
				for(int i = 0; i < al.size(); ++i) {
					ClientThread tc = al.get(i);
					try {
					tc.sInput.close();
					tc.sOutput.close();
					tc.socket.close();
					}
					catch(IOException ioE) {
						// not much I can do
					}
				}
			}
			catch(Exception e) {
				display("Exception closing the server and clients: " + e);
			}
		}
		// something went bad
		catch (IOException e) {
            String msg = sdf.format(new Date()) + " Exception on new ServerSocket: " + e + "\n";
			display(msg);
		}
	}		
    /*
     * For the GUI to stop the server
     */
	protected void stop() {
		keepGoing = false;
		// connect to myself as Client to exit statement 
		// Socket socket = serverSocket.accept();
		try {
			new Socket("localhost", port);
		}
		catch(Exception e) {
			// nothing I can really do
		}
	}
	/*
	 * Display an event (not a message) to the console or the GUI
	 */
	private void display(String msg) {
		String time = sdf.format(new Date()) + " " + msg;
		if(sg == null)
			System.out.println(time);
		else
			sg.appendEvent(time + "\n");
	}
	/*
	 *  to broadcast a message to all Clients
	 */
	private synchronized void broadcast(String message) {
		// add HH:mm:ss and \n to the message
		String time = sdf.format(new Date());
		String messageLf = time + " " + message + "\n";
		// display message on console or GUI
		if(sg == null)
			System.out.print(messageLf);
		else
			sg.appendRoom(messageLf);     // append in the room window
		
		// we loop in reverse order in case we would have to remove a Client
		// because it has disconnected
		for(int i = al.size(); --i >= 0;) {
			ClientThread ct = al.get(i);
			// try to write to the Client if it fails remove it from the list
			if(!ct.writeMsg(messageLf)) {
				al.remove(i);
				display("Disconnected Client " + ct.username + " removed from list.");
			}
		}
	}

	// for a client who logoff using the LOGOUT message
	synchronized void remove(int id) {
		// scan the array list until we found the Id
		for(int i = 0; i < al.size(); ++i) {
			ClientThread ct = al.get(i);
			// found it
			if(ct.id == id) {
				al.remove(i);
				return;
			}
		}
	}
	
	/*
	 *  To run as a console application just open a console window and: 
	 * > java Server
	 * > java Server portNumber
	 * If the port number is not specified 1500 is used
	 */ 
	public static void main(String[] args) {
		// start server on port 1500 unless a PortNumber is specified 
		int portNumber = 1500;
		switch(args.length) {
			case 1:
				try {
					portNumber = Integer.parseInt(args[0]);
				}
				catch(Exception e) {
					System.out.println("Invalid port number.");
					System.out.println("Usage is: > java Server [portNumber]");
					return;
				}
			case 0:
				break;
			default:
				System.out.println("Usage is: > java Server [portNumber]");
				return;
				
		}
		// create a server object and start it
		Server server = new Server(portNumber);
		server.start();
	}

	/** One instance of this thread will run for each client */
	class ClientThread extends Thread {
		// the socket where to listen/talk
		Socket socket;
		ObjectInputStream sInput;
		ObjectOutputStream sOutput;
		// my unique id (easier for deconnection)
		int id;
		// the Username of the Client
		String username;
		// the only type of message a will receive
		ChatMessage cm;
		// the date I connect
		String date;

		// Constructore
		ClientThread(Socket socket) {
			// a unique id
			id = ++uniqueId;
			this.socket = socket;
			/* Creating both Data Stream */
			System.out.println("Thread trying to create Object Input/Output Streams");
			try
			{
				// create output first
				sOutput = new ObjectOutputStream(socket.getOutputStream());
				sInput  = new ObjectInputStream(socket.getInputStream());
				// read the username
				username = (String) sInput.readObject();
				display(username + " just connected.");
			}
			catch (IOException e) {
				display("Exception creating new Input/output Streams: " + e);
				return;
			}
			// have to catch ClassNotFoundException
			// but I read a String, I am sure it will work
			catch (ClassNotFoundException e) {
			}
            date = new Date().toString() + "\n";
		}

		// what will run forever
		public void run() {
			// to loop until LOGOUT
			boolean keepGoing = true;
			while(keepGoing) {
				// read a String (which is an object)
				try {
					cm = (ChatMessage) sInput.readObject();
				}
				catch (IOException e) {
					display(username + " Exception reading Streams: " + e);
					break;				
				}
				catch(ClassNotFoundException e2) {
					break;
				}
				// the messaage part of the ChatMessage
				String message = cm.getMessage();

				// Switch on the type of message receive
				switch(cm.getType()) {

				case ChatMessage.MESSAGE:
					broadcast(username + ": " + message);
					break;
				case ChatMessage.LOGOUT:
					display(username + " disconnected with a LOGOUT message.");
					keepGoing = false;
					break;
				case ChatMessage.WHOISIN:
					writeMsg("List of the users connected at " + sdf.format(new Date()) + "\n");
					// scan al the users connected
					for(int i = 0; i < al.size(); ++i) {
						ClientThread ct = al.get(i);
						writeMsg((i+1) + ") " + ct.username + " since " + ct.date);
					}
					break;
				}
			}
			// remove myself from the arrayList containing the list of the
			// connected Clients
			remove(id);
			close();
		}
		
		// try to close everything
		private void close() {
			// try to close the connection
			try {
				if(sOutput != null) sOutput.close();
			}
			catch(Exception e) {}
			try {
				if(sInput != null) sInput.close();
			}
			catch(Exception e) {};
			try {
				if(socket != null) socket.close();
			}
			catch (Exception e) {}
		}

		/*
		 * Write a String to the Client output stream
		 */
		private boolean writeMsg(String msg) {
			// if Client is still connected send the message to it
			if(!socket.isConnected()) {
				close();
				return false;
			}
			// write the message to the stream
			try {
				sOutput.writeObject(msg);
			}
			// if an error occurs, do not abort just inform the user
			catch(IOException e) {
				display("Error sending message to " + username);
				display(e.toString());
			}
			return true;
		}
	}
}




The Client class.

Once the Server is started you can start the Client by typing
> java Client
at the console port. That will start the Client with the username Anonymous on the localhost using port 1500. So the command is equivalent to
> java Client Anonymous 1500 localhost
You can specify any of the parameter in order
> java Client Me == > java Client Me 1500 localhost
> java Client Me 1200 == > java Client Me 1200 localhost
> java Client Me 1200 12.14.13.14 == > java Client Me 1200 12.14.13.14

Once the Client started in console mode you can enter:
- LOGOUT to logout and close the connections
- WHOISIN to receive the list of the user connected to the server
- anything else is a message that will be broadcast, with your username, to all the Clients on the room

Client.java

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

/*
 * The Client that can be run both as a console or a GUI
 */
public class Client  {

	// for I/O
	private ObjectInputStream sInput;		// to read from the socket
	private ObjectOutputStream sOutput;		// to write on the socket
	private Socket socket;

	// if I use a GUI or not
	private ClientGUI cg;
	
	// the server, the port and the username
	private String server, username;
	private int port;

	/*
	 *  Constructor called by console mode
	 *  server: the server address
	 *  port: the port number
	 *  username: the username
	 */
	Client(String server, int port, String username) {
		// which calls the common constructor with the GUI set to null
		this(server, port, username, null);
	}

	/*
	 * Constructor call when used from a GUI
	 * in console mode the ClienGUI parameter is null
	 */
	Client(String server, int port, String username, ClientGUI cg) {
		this.server = server;
		this.port = port;
		this.username = username;
		// save if we are in GUI mode or not
		this.cg = cg;
	}
	
	/*
	 * To start the dialog
	 */
	public boolean start() {
		// try to connect to the server
		try {
			socket = new Socket(server, port);
		} 
		// if it failed not much I can so
		catch(Exception ec) {
			display("Error connectiong to server:" + ec);
			return false;
		}
		
		String msg = "Connection accepted " + socket.getInetAddress() + ":" + socket.getPort();
		display(msg);
	
		/* Creating both Data Stream */
		try
		{
			sInput  = new ObjectInputStream(socket.getInputStream());
			sOutput = new ObjectOutputStream(socket.getOutputStream());
		}
		catch (IOException eIO) {
			display("Exception creating new Input/output Streams: " + eIO);
			return false;
		}

		// creates the Thread to listen from the server 
		new ListenFromServer().start();
		// Send our username to the server this is the only message that we
		// will send as a String. All other messages will be ChatMessage objects
		try
		{
			sOutput.writeObject(username);
		}
		catch (IOException eIO) {
			display("Exception doing login : " + eIO);
			disconnect();
			return false;
		}
		// success we inform the caller that it worked
		return true;
	}

	/*
	 * To send a message to the console or the GUI
	 */
	private void display(String msg) {
		if(cg == null)
			System.out.println(msg);      // println in console mode
		else
			cg.append(msg + "\n");		// append to the ClientGUI JTextArea (or whatever)
	}
	
	/*
	 * To send a message to the server
	 */
	void sendMessage(ChatMessage msg) {
		try {
			sOutput.writeObject(msg);
		}
		catch(IOException e) {
			display("Exception writing to server: " + e);
		}
	}

	/*
	 * When something goes wrong
	 * Close the Input/Output streams and disconnect not much to do in the catch clause
	 */
	private void disconnect() {
		try { 
			if(sInput != null) sInput.close();
		}
		catch(Exception e) {} // not much else I can do
		try {
			if(sOutput != null) sOutput.close();
		}
		catch(Exception e) {} // not much else I can do
        try{
			if(socket != null) socket.close();
		}
		catch(Exception e) {} // not much else I can do
		
		// inform the GUI
		if(cg != null)
			cg.connectionFailed();
			
	}
	/*
	 * To start the Client in console mode use one of the following command
	 * > java Client
	 * > java Client username
	 * > java Client username portNumber
	 * > java Client username portNumber serverAddress
	 * at the console prompt
	 * If the portNumber is not specified 1500 is used
	 * If the serverAddress is not specified "localHost" is used
	 * If the username is not specified "Anonymous" is used
	 * > java Client 
	 * is equivalent to
	 * > java Client Anonymous 1500 localhost 
	 * are eqquivalent
	 * 
	 * In console mode, if an error occurs the program simply stops
	 * when a GUI id used, the GUI is informed of the disconnection
	 */
	public static void main(String[] args) {
		// default values
		int portNumber = 1500;
		String serverAddress = "localhost";
		String userName = "Anonymous";

		// depending of the number of arguments provided we fall through
		switch(args.length) {
			// > javac Client username portNumber serverAddr
			case 3:
				serverAddress = args[2];
			// > javac Client username portNumber
			case 2:
				try {
					portNumber = Integer.parseInt(args[1]);
				}
				catch(Exception e) {
					System.out.println("Invalid port number.");
					System.out.println("Usage is: > java Client [username] [portNumber] [serverAddress]");
					return;
				}
			// > javac Client username
			case 1: 
				userName = args[0];
			// > java Client
			case 0:
				break;
			// invalid number of arguments
			default:
				System.out.println("Usage is: > java Client [username] [portNumber] {serverAddress]");
			return;
		}
		// create the Client object
		Client client = new Client(serverAddress, portNumber, userName);
		// test if we can start the connection to the Server
		// if it failed nothing we can do
		if(!client.start())
			return;
		
		// wait for messages from user
		Scanner scan = new Scanner(System.in);
		// loop forever for message from the user
		while(true) {
			System.out.print("> ");
			// read message from user
			String msg = scan.nextLine();
			// logout if message is LOGOUT
			if(msg.equalsIgnoreCase("LOGOUT")) {
				client.sendMessage(new ChatMessage(ChatMessage.LOGOUT, ""));
				// break to do the disconnect
				break;
			}
			// message WhoIsIn
			else if(msg.equalsIgnoreCase("WHOISIN")) {
				client.sendMessage(new ChatMessage(ChatMessage.WHOISIN, ""));				
			}
			else {				// default to ordinary message
				client.sendMessage(new ChatMessage(ChatMessage.MESSAGE, msg));
			}
		}
		// done disconnect
		client.disconnect();	
	}

	/*
	 * a class that waits for the message from the server and append them to the JTextArea
	 * if we have a GUI or simply System.out.println() it in console mode
	 */
	class ListenFromServer extends Thread {

		public void run() {
			while(true) {
				try {
					String msg = (String) sInput.readObject();
					// if console mode print the message and add back the prompt
					if(cg == null) {
						System.out.println(msg);
						System.out.print("> ");
					}
					else {
						cg.append(msg);
					}
				}
				catch(IOException e) {
					display("Server has close the connection: " + e);
					if(cg != null) 
						cg.connectionFailed();
					break;
				}
				// can't happen with a String object but need the catch anyhow
				catch(ClassNotFoundException e2) {
				}
			}
		}
	}
}



The GUI is a simple GUI using JTextArea don't expect fancy fonts, colors, Icons,... I kept it as simple as possible.

The ClientGUI class.

This is a simple GUI. It is a BorderLayout with in the NORTH region an editable JTextField containing the port number the Server should listen to and 2 buttons to Start/Stop the Server.
The CENTER region contains two JScrollPane both containing a JTextArea. The first JTextArea contains the messages exchanged in the ChatRoom, basically what the Clients see. The secong JTextArea contains event messages: who login, who logout, error messages, and so on
To execute that GUI type
> java ServerGUI
at the console prompt

ServerGUI.Java
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;

/*
 * The server as a GUI
 */
public class ServerGUI extends JFrame implements ActionListener, WindowListener {
	
	private static final long serialVersionUID = 1L;
	// the stop and start buttons
	private JButton stopStart;
	// JTextArea for the chat room and the events
	private JTextArea chat, event;
	// The port number
	private JTextField tPortNumber;
	// my server
	private Server server;
	
	
	// server constructor that receive the port to listen to for connection as parameter
	ServerGUI(int port) {
		super("Chat Server");
		server = null;
		// in the NorthPanel the PortNumber the Start and Stop buttons
		JPanel north = new JPanel();
		north.add(new JLabel("Port number: "));
		tPortNumber = new JTextField("  " + port);
		north.add(tPortNumber);
		// to stop or start the server, we start with "Start"
		stopStart = new JButton("Start");
		stopStart.addActionListener(this);
		north.add(stopStart);
		add(north, BorderLayout.NORTH);
		
		// the event and chat room
		JPanel center = new JPanel(new GridLayout(2,1));
		chat = new JTextArea(80,80);
		chat.setEditable(false);
		appendRoom("Chat room.\n");
		center.add(new JScrollPane(chat));
		event = new JTextArea(80,80);
		event.setEditable(false);
		appendEvent("Events log.\n");
		center.add(new JScrollPane(event));	
		add(center);
		
		// need to be informed when the user click the close button on the frame
		addWindowListener(this);
		setSize(400, 600);
		setVisible(true);
	}		

	// append message to the two JTextArea
	// position at the end
	void appendRoom(String str) {
		chat.append(str);
		chat.setCaretPosition(chat.getText().length() - 1);
	}
	void appendEvent(String str) {
		event.append(str);
		event.setCaretPosition(chat.getText().length() - 1);
		
	}
	
	// start or stop where clicked
	public void actionPerformed(ActionEvent e) {
		// if running we have to stop
		if(server != null) {
			server.stop();
			server = null;
			tPortNumber.setEditable(true);
			stopStart.setText("Start");
			return;
		}
      	// OK start the server	
		int port;
		try {
			port = Integer.parseInt(tPortNumber.getText().trim());
		}
		catch(Exception er) {
			appendEvent("Invalid port number");
			return;
		}
		// ceate a new Server
		server = new Server(port, this);
		// and start it as a thread
		new ServerRunning().start();
		stopStart.setText("Stop");
		tPortNumber.setEditable(false);
	}
	
	// entry point to start the Server
	public static void main(String[] arg) {
		// start server default port 1500
		new ServerGUI(1500);
	}

	/*
	 * If the user click the X button to close the application
	 * I need to close the connection with the server to free the port
	 */
	public void windowClosing(WindowEvent e) {
		// if my Server exist
		if(server != null) {
			try {
				server.stop();			// ask the server to close the conection
			}
			catch(Exception eClose) {
			}
			server = null;
		}
		// dispose the frame
		dispose();
		System.exit(0);
	}
	// I can ignore the other WindowListener method
	public void windowClosed(WindowEvent e) {}
	public void windowOpened(WindowEvent e) {}
	public void windowIconified(WindowEvent e) {}
	public void windowDeiconified(WindowEvent e) {}
	public void windowActivated(WindowEvent e) {}
	public void windowDeactivated(WindowEvent e) {}

	/*
	 * A thread to run the Server
	 */
	class ServerRunning extends Thread {
		public void run() {
			server.start();         // should execute until if fails
			// the server failed
			stopStart.setText("Start");
			tPortNumber.setEditable(true);
			appendEvent("Server crashed\n");
			server = null;
		}
	}

}



The ClientGUI class.

This is the GUI for the Client. Also a BorderLayout. In the NORTH region two JTextField to enter the host name of the Server and the port number it is listening to.
The CENTER region contains a JScrollPane with a JTextArea that contains the messages exchanged in the ChatRoom.
The SOUTH region conatisn 3 buttons: "Login", "Logout", "Who is in".

To start the Client type
>java ClientGUI
at the command prompt

ClientGUI.java

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


/*
 * The Client with its GUI
 */
public class ClientGUI extends JFrame implements ActionListener {

	private static final long serialVersionUID = 1L;
	// will first hold "Username:", later on "Enter message"
	private JLabel label;
	// to hold the Username and later on the messages
	private JTextField tf;
	// to hold the server address an the port number
	private JTextField tfServer, tfPort;
	// to Logout and get the list of the users
	private JButton login, logout, whoIsIn;
	// for the chat room
	private JTextArea ta;
	// if it is for connection
	private boolean connected;
	// the Client object
	private Client client;
	// the default port number
	private int defaultPort;
	private String defaultHost;

	// Constructor connection receiving a socket number
	ClientGUI(String host, int port) {

		super("Chat Client");
		defaultPort = port;
		defaultHost = host;
		
		// The NorthPanel with:
		JPanel northPanel = new JPanel(new GridLayout(3,1));
		// the server name anmd the port number
		JPanel serverAndPort = new JPanel(new GridLayout(1,5, 1, 3));
		// the two JTextField with default value for server address and port number
		tfServer = new JTextField(host);
		tfPort = new JTextField("" + port);
		tfPort.setHorizontalAlignment(SwingConstants.RIGHT);

		serverAndPort.add(new JLabel("Server Address:  "));
		serverAndPort.add(tfServer);
		serverAndPort.add(new JLabel("Port Number:  "));
		serverAndPort.add(tfPort);
		serverAndPort.add(new JLabel(""));
		// adds the Server an port field to the GUI
		northPanel.add(serverAndPort);

		// the Label and the TextField
		label = new JLabel("Enter your username below", SwingConstants.CENTER);
		northPanel.add(label);
		tf = new JTextField("Anonymous");
		tf.setBackground(Color.WHITE);
		northPanel.add(tf);
		add(northPanel, BorderLayout.NORTH);

		// The CenterPanel which is the chat room
		ta = new JTextArea("Welcome to the Chat room\n", 80, 80);
		JPanel centerPanel = new JPanel(new GridLayout(1,1));
		centerPanel.add(new JScrollPane(ta));
		ta.setEditable(false);
		add(centerPanel, BorderLayout.CENTER);

		// the 3 buttons
		login = new JButton("Login");
		login.addActionListener(this);
		logout = new JButton("Logout");
		logout.addActionListener(this);
		logout.setEnabled(false);		// you have to login before being able to logout
		whoIsIn = new JButton("Who is in");
		whoIsIn.addActionListener(this);
		whoIsIn.setEnabled(false);		// you have to login before being able to Who is in

		JPanel southPanel = new JPanel();
		southPanel.add(login);
		southPanel.add(logout);
		southPanel.add(whoIsIn);
		add(southPanel, BorderLayout.SOUTH);

		setDefaultCloseOperation(EXIT_ON_CLOSE);
		setSize(600, 600);
		setVisible(true);
		tf.requestFocus();

	}

	// called by the Client to append text in the TextArea 
	void append(String str) {
		ta.append(str);
		ta.setCaretPosition(ta.getText().length() - 1);
	}
	// called by the GUI is the connection failed
	// we reset our buttons, label, textfield
	void connectionFailed() {
		login.setEnabled(true);
		logout.setEnabled(false);
		whoIsIn.setEnabled(false);
		label.setText("Enter your username below");
		tf.setText("Anonymous");
		// reset port number and host name as a construction time
		tfPort.setText("" + defaultPort);
		tfServer.setText(defaultHost);
		// let the user change them
		tfServer.setEditable(false);
		tfPort.setEditable(false);
		// don't react to a <CR> after the username
		tf.removeActionListener(this);
		connected = false;
	}
		
	/*
	* Button or JTextField clicked
	*/
	public void actionPerformed(ActionEvent e) {
		Object o = e.getSource();
		// if it is the Logout button
		if(o == logout) {
			client.sendMessage(new ChatMessage(ChatMessage.LOGOUT, ""));
			return;
		}
		// if it the who is in button
		if(o == whoIsIn) {
			client.sendMessage(new ChatMessage(ChatMessage.WHOISIN, ""));				
			return;
		}

		// ok it is coming from the JTextField
		if(connected) {
			// just have to send the message
			client.sendMessage(new ChatMessage(ChatMessage.MESSAGE, tf.getText()));				
			tf.setText("");
			return;
		}
		

		if(o == login) {
			// ok it is a connection request
			String username = tf.getText().trim();
			// empty username ignore it
			if(username.length() == 0)
				return;
			// empty serverAddress ignore it
			String server = tfServer.getText().trim();
			if(server.length() == 0)
				return;
			// empty or invalid port numer, ignore it
			String portNumber = tfPort.getText().trim();
			if(portNumber.length() == 0)
				return;
			int port = 0;
			try {
				port = Integer.parseInt(portNumber);
			}
			catch(Exception en) {
				return;   // nothing I can do if port number is not valid
			}

			// try creating a new Client with GUI
			client = new Client(server, port, username, this);
			// test if we can start the Client
			if(!client.start()) 
				return;
			tf.setText("");
			label.setText("Enter your message below");
			connected = true;
			
			// disable login button
			login.setEnabled(false);
			// enable the 2 buttons
			logout.setEnabled(true);
			whoIsIn.setEnabled(true);
			// disable the Server and Port JTextField
			tfServer.setEditable(false);
			tfPort.setEditable(false);
			// Action listener for when the user enter a message
			tf.addActionListener(this);
		}

	}

	// to start the whole thing the server
	public static void main(String[] args) {
		new ClientGUI("localhost", 1500);
	}

}




Enjoy

*Edited: added a "\n" after the String date in the Server thread. Thanks to blackcompe*Edited: add a WindowListener to the ServerGUI to close the Server if the user click the X button. Thanks again to blackcompe

Can we create same functionality for chat application in JSP and servlet??? if you have some sample code please let me knoe
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