1 import javax.swing.*;
 2 import java.awt.*;
 3 import java.io.*;
 4 import java.net.*;
 5 import java.awt.event.*;
 6 
 7 public class ChatClient {
 8     private JTextArea incoming;
 9     private JTextField outgoing;
10     private PrintWriter writer;
11     private BufferedReader reader;
12         
13     public static void main(String[] args) {
14         ChatClient client = new ChatClient();
15         client.go();
16     }
17     
18     private void go() {
19         build_gui();
20         setup_net();
21     }
22     
23     private void build_gui() {
24         JFrame frame = new JFrame("Chat Client");
25         JPanel panel = new JPanel();
26         
27         incoming = new JTextArea(15, 50);
28         incoming.setLineWrap(true);
29         incoming.setWrapStyleWord(true);
30         incoming.setEditable(false);
31         JScrollPane qScroller = new JScrollPane(incoming);
32         qScroller.setVerticalScrollBarPolicy(ScrollPaneConstants.VERTICAL_SCROLLBAR_ALWAYS);
33         qScroller.setHorizontalScrollBarPolicy(ScrollPaneConstants.HORIZONTAL_SCROLLBAR_NEVER);
34         panel.add(incoming);
35         
36         outgoing = new JTextField(20);
37         panel.add(outgoing);
38         
39         JButton button = new JButton("Send");
40         button.addActionListener(new SendButtonListener());
41         panel.add(button);
42         
43         frame.add(BorderLayout.CENTER, panel);
44         frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
45         frame.setSize(600, 400);        
46         frame.setVisible(true);
47     }
48     
49     public class SendButtonListener implements ActionListener {
50         public void actionPerformed(ActionEvent a) {
51             String msg = outgoing.getText();
52             try {
53                 writer.println(msg);
54                 writer.flush();
55             } catch (Exception ex) { ex.printStackTrace(); }
56             outgoing.setText("");
57             outgoing.requestFocus();
58         }
59     }
60     
61     class ReceiveThreadJob implements Runnable {
62         public void run() {
63             String msg;
64             try {
65                 while ( (msg = reader.readLine()) != null ) {
66                     incoming.append(msg + "\n");
67                 }
68             } catch (IOException ex) { System.out.println("server disconnected"); }        
69         }
70     }
71     
72     private void setup_net() {
73         try {
74             Socket s = new Socket("127.0.0.1", 4242);
75             writer = new PrintWriter(s.getOutputStream());
76             InputStreamReader streamReader = new InputStreamReader( s.getInputStream() );
77             reader = new BufferedReader( streamReader );    
78 
79             Runnable receive_thread_job = new ReceiveThreadJob();
80             Thread receive_thread = new Thread( receive_thread_job );
81             receive_thread.start();
82             
83         } catch (IOException ex) {
84             ex.printStackTrace();
85         }
86     }
87 }

 1 import java.io.*;
 2 import java.net.*;
 3 import java.util.ArrayList;
 4 
 5 public class ChatServer {
 6     BufferedReader reader;
 7     ArrayList<PrintWriter> writer_array = new ArrayList<PrintWriter>();
 8 
 9     public static void main(String[] args) {
10         ChatServer server = new ChatServer();
11         server.go();
12     }
13     
14     private void go() {
15         setup_net();
16     }
17     
18     private void setup_net() {
19         try {
20             ServerSocket serverSock = new ServerSocket(4242);
21             while (true) {
22                 Socket s = serverSock.accept();
23                 System.out.println("client connected");
24                 InputStreamReader streamReader = new InputStreamReader( s.getInputStream() );
25                 reader = new BufferedReader( streamReader );                            
26                 PrintWriter writer = new PrintWriter(s.getOutputStream());
27                 writer_array.add(writer);                
28                 Runnable server_proc_thread_job = new ServerProcThreadJob();
29                 Thread server_proc = new Thread( server_proc_thread_job );
30                 server_proc.start();
31             }
32         } catch (IOException ex) {
33             ex.printStackTrace();
34         }
35     }
36     
37     class ServerProcThreadJob implements Runnable {
38         public void run() {
39             String msg;
40             try {
41                 while ( (msg = reader.readLine()) != null ) {
42                     System.out.println(msg);
43                     for ( PrintWriter writer: writer_array ) {
44                         writer.println(msg);
45                         writer.flush();
46                     }
47                 }
48             } catch (IOException ex) { System.out.println("client disconnected"); }
49         }
50     }
51 }