diff --git a/src/chat/ClientWindow.java b/src/chat/ClientWindow.java
index 7f5d5a6..165bbe6 100644
--- a/src/chat/ClientWindow.java
+++ b/src/chat/ClientWindow.java
@@ -1,18 +1,16 @@
 package chat;
+
 import java.net.*;
+
 import javax.swing.*;
 
 import java.awt.*;
 import java.awt.event.*;
 
+import java.io.*;
+import java.util.*;
 
-import java.io.BufferedReader;
-import java.io.IOException;
-import java.io.InputStreamReader;
-import java.io.PrintWriter;
-import java.net.ServerSocket;
-import java.net.Socket;
-import java.net.DatagramSocket;
+import chat.User;
 
 class SendThread extends Thread {
 	String username;
@@ -88,57 +86,76 @@ class ReceiveThread extends Thread {
 	}
 }
 
-/*class PopupWindow implements ActionListener {
-	JFrame popupWindow;
-	JPanel popupPanel;
-	JButton submitButton;
-	JPanel fieldLine[] = new JPanel[4];
-	JTextField inputField[] = new JTextField[4];
-	JLabel fieldLabel[] = new JLabel[4];
+class ConnectionListenerThread extends Thread {
 	
-	PopupWindow()
+	int port;
+	JTextArea displayArea;
+	User user;
+	
+	ConnectionListenerThread(User in_user)
 	{
-		fieldLabel[0] = new JLabel("Destination IP address");
-		fieldLabel[1] = new JLabel("Destination port");
-		fieldLabel[2] = new JLabel("Source port");
-		fieldLabel[3] = new JLabel("Username");
+		user = in_user;
+	}
+	public void run()
+	{
+		Boolean exit = false;
+		byte[] buffer = new byte[100];
+		DatagramPacket request = new DatagramPacket(buffer, buffer.length);
+		DatagramPacket responsePacket1;
+		DatagramPacket responsePacket2;
 		
-		popupPanel = new JPanel(new GridLayout(5,1));
+		DatagramSocket requestSocket;
+		DatagramSocket responseSocket;
 		
-		for(int i = 0;i < 4; i ++)
+		ByteArrayOutputStream bStream = new ByteArrayOutputStream();
+		ObjectOutput oo = new ObjectOutputStream(bStream); 
+		
+		String username;
+		
+		byte[] response1, response2;
+		try
 		{
-			inputField[i] = new JTextField();
-			fieldLine[i] = new JPanel(new GridLayout(1,2));
-			fieldLine[i].add(fieldLabel[i]);
-			fieldLine[i].add(inputField[i]);
-			popupPanel.add(fieldLine[i]);
+			requestSocket = new DatagramSocket(1234);	
+			responseSocket = new DatagramSocket();
+		
+			while(!exit)
+			{
+				try
+				{
+					requestSocket.receive(request);
+					username = new String(request.getData(), 0, request.getLength());
+					InetAddress clientAddress= request.getAddress();
+					
+					oo.writeObject(user.getUsers());
+					response1 = bStream.toByteArray();
+					responsePacket1 = new DatagramPacket(response1, response1.length, clientAddress, 1235);
+					responseSocket.send(responsePacket1);
+					
+					oo.writeObject(user.getHosts());
+					response2 = bStream.toByteArray();
+					responsePacket2 = new DatagramPacket(response2, response2.length, clientAddress, 1236);
+					responseSocket.send(responsePacket2);
+					if(!user.findUser(username))
+						user.add_to_known_users(username, clientAddress.toString());
+					
+				}
+				catch(SocketTimeoutException e)
+				{
+	    		
+				}
+	    	}
+		}
+		catch(Exception e)
+		{
+			System.out.println("nik!!");
 		}
-		
-		submitButton = new JButton("OK");
-
-		popupPanel.add(submitButton);
-		
-		popupWindow = new JFrame();
-		popupWindow.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
-        popupWindow.setSize(new Dimension(640, 480));
-		
-        popupWindow.getContentPane().add(popupPanel, BorderLayout.CENTER);
-        
-        
-		popupWindow.pack();
-        popupWindow.setVisible(true);
 	}
-	
-	public void actionPerformed(ActionEvent event) {
-	    	
-	}
-}*/
-public class ClientWindow implements ActionListener {	
+}
 
-	
+
+public class ClientWindow implements ActionListener {		
 	JFrame chatWindow;
 	
-	
 	JPanel chatPanel;
 	JTextArea chatText;
 	JScrollPane textScroll;
@@ -147,14 +164,66 @@ public class ClientWindow implements ActionListener {
 	JTextField messageField;
 	JButton sendButton;
 	
-    String address;
-    int sport;
-    int dport;
-    String username;
+    User user;
 	
 	ClientWindow()
 	{
-		chatWindow  = new JFrame("Système de clavardage 2.0.1");
+        String username;
+        Boolean connected = false;
+        DatagramSocket connectionSocket;
+        DatagramSocket userListSocket;
+        DatagramSocket hostListSocket;
+        
+        DatagramPacket connectionRequest;
+        DatagramPacket userListPacket;
+        DatagramPacket hostListPacket;
+        
+        ObjectInputStream userListStream;
+        ObjectInputStream hostListStream;
+        
+        ArrayList<String> userList;
+        ArrayList<String> hostList;
+               
+        username = JOptionPane.showInputDialog(chatWindow,
+				"Enter a username",
+				"POPOPOPOPUPUPOPOPUP",
+				JOptionPane.PLAIN_MESSAGE);
+        
+        while (!connected)
+        {
+            connectionSocket = new DatagramSocket();
+            userListSocket = new DatagramSocket(1235);
+            hostListSocket = new DatagramSocket(1236);
+            
+            connectionRequest = new DatagramPacket(username.getBytes(), username.length(),
+            													InetAddress.getByName("192.168.1.255"), 1234);
+            
+            try
+            {               
+            	userListStream = new ObjectInputStream(new ByteArrayInputStream(userListPacket.getData()));
+            	hostListStream = new ObjectInputStream(new ByteArrayInputStream(hostListPacket.getData()));
+            	
+            	userList = (ArrayList<String>) userListStream.readObject();
+            	hostList = (ArrayList<String>) hostListStream.readObject();
+            	
+            	if (userList.indexOf(username) != -1)
+            		connected = false;
+            	else
+            	{
+            		for(int i = 0;i < userList.size();i ++)
+                	{
+                		user.add_to_known_users(userList.get(i), hostList.get(i));
+                	}
+            		connected = true;
+            	}
+            }
+          	catch(SocketTimeoutException e)
+            {
+          		connected = true;
+            }
+        }
+        
+        chatWindow  = new JFrame("Système de clavardage 2.0.1");
 		
 		chatPanel = new JPanel(new GridLayout(2, 2));
 		chatText = new JTextArea(1,1);
@@ -182,25 +251,8 @@ public class ClientWindow implements ActionListener {
         chatWindow.getContentPane().add(chatPanel, BorderLayout.CENTER);
         
 
-        //Display the window.
 
-        
-		address = JOptionPane.showInputDialog(chatWindow,
-					"Enter the destination address",
-					"POPOPOPOPUPUPOPOPUP",
-					JOptionPane.PLAIN_MESSAGE);
-		sport = Integer.parseInt(JOptionPane.showInputDialog(chatWindow,
-					"Enter the source port",
-					"POPOPOPOPUPUPOPOPUP",
-					JOptionPane.PLAIN_MESSAGE));
-        dport = Integer.parseInt(JOptionPane.showInputDialog(chatWindow,
-					"Enter the destination port",
-					"POPOPOPOPUPUPOPOPUP",
-					JOptionPane.PLAIN_MESSAGE));
-        username = JOptionPane.showInputDialog(chatWindow,
-            									"Enter a username",
-            									"POPOPOPOPUPUPOPOPUP",
-            									JOptionPane.PLAIN_MESSAGE);
+        //Display the window.
         chatWindow.pack();
         chatWindow.setVisible(true);
             
diff --git a/src/chat/User.java b/src/chat/User.java
index 7165cf6..dbead23 100644
--- a/src/chat/User.java
+++ b/src/chat/User.java
@@ -1,8 +1,26 @@
 package chat;
 
+import java.io.*; 
+import java.util.*; 
+
 public class User {
 
-	private String pseudo = null;
+	private String pseudo;
+	private ArrayList<String>  knownUsers;
+	private ArrayList<String>  knownHosts;
+	
+	User(String in_pseudo)
+	{
+		pseudo = in_pseudo;
+		knownUsers = new ArrayList<String>();
+		knownHosts = new ArrayList<String>();
+	}
+	
+	public void add_to_known_users(String name, String address)
+	{
+		knownUsers.add(name);
+		knownHosts.add(address);
+	}
 	public void setpseudo(String pseudo)
 	{
 		this.pseudo = pseudo;
@@ -11,4 +29,16 @@ public class User {
 	{
 		return pseudo;
 	}
+	public Boolean findUser(String username)
+	{
+		return (knownUsers.indexOf(username) != -1);
+	}
+	public ArrayList<String> getUsers()
+	{
+		return knownUsers;
+	}
+	public ArrayList<String> getHosts()
+	{
+		return knownHosts;
+	}
 }