Client to client chat application

[Salman Mushtaq]

Hi everyone , i develop simple client to client chat application , but there will be problem when server is connect , then i run client code , it ask name as i enter name and click ok it will return null and terminates now what i can i do i cannot understand because of pressure .
Here is the code
Sever

import java.util.*;
import java.io.*;
import java.net.*;
import static java.lang.System.out;
public class ChatServer
{
	public static void main(String args[]) throws Exception
	{

		new ChatServer().createServer();
	}
			Vector<String> users = new Vector<String>();
			Vector<Manageuser> clients = new Vector<Manageuser>();

	public void createServer() throws Exception
	{
		ServerSocket server = new ServerSocket(80,10);
		out.println("Server in now running");
		while(true)
		{
			Socket client = server.accept();
			Manageuser c = new Manageuser(client);
			clients.add(c);
		}
	}
	public void sendToAll(String user , String message)
	{
		for(Manageuser c : clients)
		{
			if(!c.getchatusers().equals(user))
			{
				c.sendMessage(user,message);
			}
		}
	}
	class Manageuser extends Thread
	{
		String gotuser = "";
		BufferedReader input;
		PrintWriter output;
		public Manageuser(Socket client) throws Exception
		{
			input = new BufferedReader(new InputStreamReader(client.getInputStream()));
			output = new PrintWriter(client.getOutputStream(),true);
			gotuser = input.readLine();
			start();
		}
		public void sendMessage(String chatuser , String chatmsg)
		{
			output.println(chatuser + " Ne kaha hai " + chatmsg);
		}
		public String getchatusers()
		{
			return gotuser;
		}
		// OverRide Thread Method
		public void run()
		{
			String line;
			try
			{
				while(true)
				{
					line = input.readLine();
					if(line.equals("end"))
					{
						clients.remove(this);
						users.remove(gotuser);
						break;
					}
					sendToAll(gotuser , line);
				}
			}
			catch(Exception ex)
			{
				System.out.println(ex.getMessage());
			}
		}
	}
}

Client

import javax.swing.*;

import java.awt.*;
import java.awt.event.*;
import java.io.*;
import java.net.*;
import static java.lang.System.out;

public final class ChatUsers extends JFrame implements ActionListener
{
	String username;
	BufferedReader br;
	PrintWriter pw;
	JTextArea chatmsg;
	JTextField chatip;
	JButton send,exit;
	Socket chatusers;
	public ChatUsers(String uname , String servername) throws Exception
	{
		super(uname);
		this.username = username;
		chatusers = new Socket (servername,80);
		br = new BufferedReader(new InputStreamReader(chatusers.getInputStream()));
		pw = new PrintWriter (chatusers.getOutputStream(),true);
		pw.println(uname);
		buildInterface();
		new MessageThread().start();
	}
	public void buildInterface()
	{
		send = new JButton("Send");
		exit = new JButton("Exit");
		chatmsg = new JTextArea();
		chatmsg.setRows(300);
		chatmsg.setColumns(50);
		chatip = new JTextField(50);
		JScrollPane sp = JScrollPane(chatmsg , JScrollPane.VERTICAL_SCROLLBAR_AS_NEEDED , JScrollPane.HORIZONTAL_SCROLLBAR_AS_NEEDED);
		add(sp , "Center");
		JPanel bp = new JPanel(new FlowLayout());
		bp.add(chatip);
		bp.add(send);
		bp.add(exit);
		bp.setBackground(Color.LIGHT_GRAY);
		bp.setName("Cheetah Software House");
		add(bp , "North");
		send.addActionListener(this);
		exit.addActionListener(this);
		setSize(500,300);
		setVisible(true);
		//pack();
	}
	private JScrollPane JScrollPane(JTextArea chatmsg2,
			int verticalScrollbarAsNeeded, int horizontalScrollbarAsNeeded) {
		// TODO Auto-generated method stub
		return null;
	}
	public void actionPerformed(ActionEvent evt)
	{
		if(evt.getSource()==exit)
		{
			pw.println("The End");
			System.exit(0);
		}
		else
		{
			pw.println(chatip.getText());
			chatip.setText(null);
		}
	}
	public static void main(String args[]) throws Exception
	{
		String setUserName = JOptionPane.showInputDialog(null,"Enter your name :", "Cheetah Software House" , JOptionPane.PLAIN_MESSAGE);
		String servername = "localhost";
		try
		{
			new ChatUsers(setUserName , servername);
		}
		catch(Exception ex)
		{
			System.out.println(ex.getMessage());
		}
	}
	class MessageThread extends Thread
	{
		public void run()
		{
			String line;
			try
			{
				while(true)
				{
					line = br.readLine();
					chatmsg.append( line+"\n");
				}
			}
			catch(Exception ex)
			{
				System.out.println(ex.getMessage());
			}
		}
	}
}

Waiting for response

[Ulf Dittmer]

What does "it will return null" mean? What, exactly, is null, and what do you think it should be instead? TellTheDetails.