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 text_area;
 9     private PrintWriter writer;
10     private Socket s;
11         
12     public static void main(String[] args) {
13         ChatClient client = new ChatClient();
14         client.go();
15     }
16     
17     private void go() {
18         build_gui();
19         setup_net();
20     }
21     
22     private void build_gui() {
23         JFrame frame = new JFrame("Chat Client");
24         JPanel panel = new JPanel();
25         text_area = new JTextArea(1, 20);
26         panel.add(text_area);
27         JButton button = new JButton("Send");
28         button.addActionListener(new SendButtonListener());
29         panel.add(button);
30         frame.add(BorderLayout.CENTER, panel);
31         frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
32         frame.setBounds(50, 50, 400, 100);
33         frame.setVisible(true);
34     }
35     
36     public class SendButtonListener implements ActionListener {
37         public void actionPerformed(ActionEvent a) {
38             String msg = text_area.getText();
39             System.out.println(msg);
40             writer.println(msg);
41             writer.flush(); //如果没有则服务器端收不到消息
42         }
43     }
44     
45     private void setup_net() {
46         try {
47             s = new Socket("127.0.0.1", 4242);
48             writer = new PrintWriter(s.getOutputStream());            
49         } catch (IOException ex) {
50             ex.printStackTrace();
51         }
52     }
53 }

 1 import java.io.*;
 2 import java.net.*;
 3 
 4 public class ChatServer {
 5 
 6     public static void main(String[] args) {
 7         ChatServer server = new ChatServer();
 8         server.go();
 9     }
10     
11     private void go() {
12         setup_net();
13     }
14     
15     private void setup_net() {
16         try {
17             ServerSocket serverSock = new ServerSocket(4242);
18             while (true) {
19                 Socket s = serverSock.accept();
20                 System.out.println("client connected");
21                 InputStreamReader streamReader = new InputStreamReader( s.getInputStream() );
22                 BufferedReader reader = new BufferedReader( streamReader );
23                 String msg;
24                 try { //如果没有这个try则当客户端关闭后会异常退出
25                     while ( (msg = reader.readLine()) != null ) {
26                         System.out.println(msg);
27                     }
28                 } catch (IOException ex) { System.out.println("client disconnected"); }
29             }
30         } catch (IOException ex) {
31             ex.printStackTrace();
32         }
33     }
34 }