Lỗi java.lang.NullPointerException trong chat

Class chatjavaswing

package chat;
import java.awt.EventQueue;
import javax.swing.JFrame;
import javax.swing.JTextArea;
import javax.swing.JTextField;
import java.awt.Font;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.net.ServerSocket;
import java.net.Socket;

import javax.swing.JButton;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;

public class chatjavaswing {

	private JFrame frame;
	private JTextField mess;
    static JTextArea arena;
    static ServerSocket ss;
    static Socket s;
    static DataInputStream in;
    static DataOutputStream out;
	/**
	 * Launch the application.
	 */
	private void initialize() {
		frame = new JFrame("people 1");
		frame.setBounds(100, 100, 450, 300);
		frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		frame.getContentPane().setLayout(null);
		
	    arena = new JTextArea();
		arena.setEditable(false);
		arena.setBounds(0, 0, 434, 206);
		frame.getContentPane().add(arena);
		
		mess = new JTextField();
		mess.setFont(new Font("Sylfaen", Font.PLAIN, 22));
		mess.setBounds(0, 217, 260, 33);
		frame.getContentPane().add(mess);
		mess.setColumns(10);
		
		JButton btnNewButton = new JButton("Sent");
		btnNewButton.addActionListener(new ActionListener() {
			public void actionPerformed(ActionEvent e) {
				try {
					String magout="";
					magout=mess.getText().trim();
					out.writeUTF(magout);
					}catch (Exception ex) {
					ex.printStackTrace();
				}
			}
		});
		btnNewButton.setBounds(286, 219, 89, 23);
		frame.getContentPane().add(btnNewButton);
	}
	public chatjavaswing() {
		initialize();
	}
	public static void main(String[] args) {
		EventQueue.invokeLater(new Runnable() {
			public void run() {
				try {
					chatjavaswing window = new chatjavaswing();
					window.frame.setVisible(true);
				} catch (Exception e) {
					e.printStackTrace();
				}
			}
		});
		String magin="";
		try {
			ss = new ServerSocket(52919);
			s=ss.accept();
			in=new DataInputStream(s.getInputStream());
			out=new DataOutputStream(s.getOutputStream());
			while(magin.equals("exit")) {
				magin=in.readUTF();
				arena.setText(arena.getText().trim()+"\n"+magin);
				}
		}catch (Exception ex) {
			ex.printStackTrace();
		}
	}
}

class chatjavaswing1

package chat;

import java.awt.EventQueue;

import javax.swing.JFrame;
import javax.swing.JTextArea;
import javax.swing.JTextField;
import java.awt.Font;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.net.Socket;

import javax.swing.JButton;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;

public class chatjavaswing1 {

	private JFrame frame;
	private JTextField mess;
    static JTextArea arena;
    static Socket s;
    static DataInputStream in;
    static DataOutputStream out;
	private void initialize() {
		frame = new JFrame("people 2");
		frame.setBounds(100, 100, 450, 300);
		frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		frame.getContentPane().setLayout(null);
		
		arena = new JTextArea();
		arena.setEditable(false);
		arena.setBounds(0, 0, 434, 206);
		frame.getContentPane().add(arena);
		
		mess = new JTextField();
		mess.setFont(new Font("Sylfaen", Font.PLAIN, 22));
		mess.setBounds(0, 217, 260, 33);
		frame.getContentPane().add(mess);
		mess.setColumns(10);
		
		JButton btnNewButton = new JButton("Sent");
		btnNewButton.addActionListener(new ActionListener() {
			public void actionPerformed(ActionEvent e) {
				try {
					String magout="";
					magout=mess.getText().trim();
					out.writeUTF(magout);
					}catch (Exception ex) {
					ex.printStackTrace();
				}
			}
		});
		btnNewButton.setBounds(286, 219, 89, 23);
		frame.getContentPane().add(btnNewButton);
	}
	public static void main(String[] args) {
		EventQueue.invokeLater(new Runnable() {
			public void run() {
				try {
					chatjavaswing1 window = new chatjavaswing1();
					window.frame.setVisible(true);
				} catch (Exception e) {
					e.printStackTrace();
				}
			}
		});
		try {
			s=new Socket("192.168.1.1",52919);
			in=new DataInputStream(s.getInputStream());
			out=new DataOutputStream(s.getOutputStream());
			String magin="";
			while(magin.equals("exit")) {
				magin=in.readUTF();
				arena.setText(arena.getText().trim()+"\n chatjavaswing:\t"+magin);
				}
		}catch (Exception ex) {
			ex.printStackTrace();
		}
	}

	/**
	 * Create the application.
	 */
	public chatjavaswing1() {
		initialize();
	}
}