The code examples show source code for a client and server application for a chat program. The client code defines functions for connecting to the server, sending and receiving messages. The server code defines functions for starting the server, accepting new connections from clients, and handling message receives and sends between connected clients. The code implements multi-threaded processing to concurrently handle multiple client connections to the server.

1. Source Code Client
/*
* To change this license header, choose License Headers in Project
Properties.
* To change this template file, choose Tools | Templates
* and open the template in the editor.
*/
package tcp;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.PrintStream;
import java.net.ServerSocket;
import java.net.Socket;
/**
*
* @author SHUBHAM
*/
public class Client {
public static void main(String args[]) throws Exception
{
Socket sk=new Socket("127.0.0.1",5000);
BufferedReader sin=new BufferedReader(new
InputStreamReader(sk.getInputStream()));
PrintStream sout=new PrintStream(sk.getOutputStream());
BufferedReader stdin=new BufferedReader(new
InputStreamReader(System.in));
String s;
while ( true )
{

2. System.out.print("Client : ");
s=stdin.readLine();
sout.println(s);
if ( s.equalsIgnoreCase("BYE") )
{
System.out.println("Connection ended by client");
break;
}
s=sin.readLine();
System.out.print("Server : "+s+"n");
}
sk.close();
sin.close();
sout.close();
stdin.close();
}
}
Source Code Server
/*
* To change this template, choose Tools | Templates
* and open the template in the editor.
*/
package syarifchatting;
import java.awt.Color;
import java.io.BufferedReader;
import java.io.BufferedWriter;

3. import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.PrintStream;
import java.net.ServerSocket;
import java.net.Socket;
import java.net.UnknownHostException;
import java.text.Normalizer.Form;
import java.util.Scanner;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.swing.JColorChooser;
import javax.swing.JOptionPane;
/**
* @author MhdSyarif
* Monday, 13 January 2014, 20 : 52 : 20 WIB
* Tugas III Matakulia Java2SE
* Mhd. Syarif | 49013075
* TKJMD - STEI - ITB
*/
public class Server extends javax.swing.JFrame implements Runnable{
int port=8080;
Socket client;
ServerSocket server;
BufferedReader Server_Reader, Client_Reader;
BufferedWriter Server_Writer, Client_Writer;

4. /**
* Creates new form Server
*/
//ServerSocket server=null;
// Socket client=null;
ExecutorService pool = null;
int clientcount=0;
// public static void main(String[] args) throws IOException {
// Server serverobj=new Server(5000);
// serverobj.startServer();
// }
Server(int port){
this.port=port;
pool = Executors.newFixedThreadPool(5);
}
public void Client() throws IOException
{
Socket sk=new Socket("127.0.0.1",5000);
BufferedReader sin=new BufferedReader(new
InputStreamReader(sk.getInputStream()));
PrintStream sout=new PrintStream(sk.getOutputStream());
BufferedReader stdin=new BufferedReader(new
InputStreamReader(System.in));
String s;
while ( true )
{
System.out.print("Client : ");

5. s=stdin.readLine();
sout.println(s);
if ( s.equalsIgnoreCase("BYE") )
{
System.out.println("Connection ended by client");
break;
}
s=sin.readLine();
System.out.print("Server : "+s+"n");
}
sk.close();
sin.close();
sout.close();
stdin.close();
}
public void startServer() throws IOException {
server=new ServerSocket(5000);
System.out.println("Server Booted");
System.out.println("Any client can stop the server by sending -1");
while(true)
{
client=server.accept();
clientcount++;
ServerThread runnable= new ServerThread(client,clientcount,this);
pool.execute(runnable);
}

6. }
private static class ServerThread implements Runnable {
Server server=null;
Socket client=null;
BufferedReader cin;
PrintStream cout;
Scanner sc=new Scanner(System.in);
int id;
String s;
ServerThread(Socket client, int count ,Server server ) throws
IOException {
this.client=client;
this.server=server;
this.id=count;
System.out.println("Connection "+id+"established with client
"+client);
cin=new BufferedReader(new
InputStreamReader(client.getInputStream()));
cout=new PrintStream(client.getOutputStream());
}
@Override
public void run() {
int x=1;
try{
while(true){

7. s=cin.readLine();
System. out.print("Client("+id+") :"+s+"n");
System.out.print("Server : ");
//s=stdin.readLine();
s=sc.nextLine();
if (s.equalsIgnoreCase("bye"))
{
cout.println("BYE");
x=0;
System.out.println("Connection ended by server");
break;
}
cout.println(s);
}
cin.close();
client.close();
cout.close();
if(x==0) {
System.out.println( "Server cleaning up." );
System.exit(0);
}
}
catch(IOException ex){
System.out.println("Error : "+ex);
}
}

8. }
public Server() {
super("www.mhdsyarif.com"); //SetTitle
initComponents();
//Menampilkan hasil ditengah window
java.awt.Dimension screenSize =
java.awt.Toolkit.getDefaultToolkit().getScreenSize();
java.awt.Dimension dialogSize = getSize();
setLocation((screenSize.width-dialogSize.width)/2,(screenSize.height-
dialogSize.height)/2);
}
//Pilihan ComboBox
private void getComboBox(){
if(ComboBox.getSelectedItem().equals("Server")){
ButtonOn.setText("On");
Username.setText("Server");
}else{
ButtonOn.setText("Connect");
Username.setText("Client");
}
}
//Koneksi client ke server
private void getClientConnec(){
try {
String ip = JOptionPane.showInputDialog(" Input IP Address");
client = new Socket(ip, port);
ComboBox.setEnabled(false);
ButtonOn.setText("Disconnect");

9. Server_Reader = new BufferedReader(new
InputStreamReader(client.getInputStream()));
Server_Writer = new BufferedWriter (new
OutputStreamWriter(client.getOutputStream()));
} catch (UnknownHostException ex) {
System.out.println("Accept Failed");
System.exit(-1);
} catch (IOException ex) {
Logger.getLogger(Form.class.getName()).log(Level.SEVERE, null,
ex);
}
}
private void getReadConnec(){
try {
try {
try {
server = new ServerSocket(port);
this.setTitle("Please Wait");
} catch (IOException ex) {
System.out.println("Could not listen");
System.exit(-1);
}
client = server.accept();
this.setTitle("Connected" + client.getInetAddress());
} catch (IOException ex) {
System.out.println("Accept Failed");
System.exit(-1);
}
Server_Reader = new BufferedReader(new
InputStreamReader(client.getInputStream()));
Server_Writer = new BufferedWriter(new
OutputStreamWriter(client.getOutputStream()));

10. } catch (IOException ex) {
System.out.println("Read Failed");
System.exit(-1);
}
}
private void getDisconnectedClient(){
try {
client.close();
Server_Reader.close();
Server_Writer.close();
ComboBox.setEnabled(true);
ButtonOn.setText("Connect");
} catch (IOException ex) {
Logger.getLogger(Form.class.getName()).log(Level.SEVERE, null,
ex);
}
}
private void getDisconnectedServer(){
try {
Server_Reader.close();
Server_Writer.close();
ButtonOn.setText("On");
this.setTitle("Disconected");
} catch (IOException ex) {
Logger.getLogger(Form.class.getName()).log(Level.SEVERE, null,
ex);
}
}

11. private void getButtonOn(){
if(ButtonOn.getText().equals("Connect"))
{
ButtonOn.setText("DIsconnect");
getClientConnec();
Thread thread1= new Thread(this);
Thread thread2= new Thread(this);
Thread thread3= new Thread(this);
Thread thread4= new Thread(this);
Thread thread5= new Thread(this);
Thread thread6= new Thread(this);
Thread thread7= new Thread(this);
Thread thread8= new Thread(this);
Thread thread9= new Thread(this);
Thread thread10= new Thread(this);
thread1.start();
thread2.start();
thread3.start();
thread4.start();
thread5.start();
thread6.start();
thread7.start();
thread8.start();
thread9.start();
thread10.start();
} else if(ComboBox.getSelectedItem().equals("Server")){
ButtonOn.setText("Off");
getReadConnec();
Thread thread1= new Thread(this);
Thread thread2= new Thread(this);

12. Thread thread3= new Thread(this);
Thread thread4= new Thread(this);
Thread thread5= new Thread(this);
Thread thread6= new Thread(this);
Thread thread7= new Thread(this);
Thread thread8= new Thread(this);
Thread thread9= new Thread(this);
Thread thread10= new Thread(this);
thread1.start();
thread2.start();
thread3.start();
thread4.start();
thread5.start();
thread6.start();
thread7.start();
thread8.start();
thread9.start();
thread10.start();
}else if(ButtonOn.getText().equals("Disconnect")){
getDisconnectedClient();
}else if(ButtonOn.getText().equals("Off")){
getDisconnectedServer();
}
}
private void getSend(){
try {
Server_Writer.write(Username.getText()+ ": "
+TextChat.getText());
Server_Writer.newLine();
Server_Writer.flush();

13. } catch (IOException ex) {
Logger.getLogger(Form.class.getName()).log(Level.SEVERE, null,
ex);
}
ListChat.add(Username.getText()+ ": " +TextChat.getText());
//jClient.setText(Username.getText());
TextChat.setText("");
}
//Background color
public void getBackgroundColor(){
Color c = JColorChooser.showDialog(null,"Background
Color",jPanel.getBackground());
jPanel.setBackground(c);
}
//Konfirmasi keluar
public void getExit(){
int confirm =JOptionPane.showConfirmDialog(this,"Are you sure will
exit this application ?","Exit
Application",JOptionPane.YES_NO_OPTION,JOptionPane.QUESTION_MESSAGE);
if (confirm == JOptionPane.YES_OPTION){
System.exit(0);
}
}
/**
* This method is called from within the constructor to initialize the
form.
* WARNING: Do NOT modify this code. The content of this method is always
* regenerated by the Form Editor.
*/
@SuppressWarnings("unchecked")

14. // <editor-fold defaultstate="collapsed" desc="Generated Code">
private void initComponents() {
Dialog = new javax.swing.JDialog();
ColorChooser = new javax.swing.JColorChooser();
jPanel = new javax.swing.JPanel();
ComboBox = new javax.swing.JComboBox();
ButtonOn = new javax.swing.JButton();
Send = new javax.swing.JToggleButton();
JUsername = new javax.swing.JLabel();
Username = new javax.swing.JTextField();
TextChat = new java.awt.TextArea();
ListChat = new java.awt.List();
jMenuBar1 = new javax.swing.JMenuBar();
File = new javax.swing.JMenu();
BackgroundColor = new javax.swing.JMenuItem();
Exit = new javax.swing.JMenuItem();
Help = new javax.swing.JMenu();
About = new javax.swing.JMenuItem();
javax.swing.GroupLayout DialogLayout = new
javax.swing.GroupLayout(Dialog.getContentPane());
Dialog.getContentPane().setLayout(DialogLayout);
DialogLayout.setHorizontalGroup(
DialogLayout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(DialogLayout.createSequentialGroup()
.addContainerGap()
.addComponent(ColorChooser,
javax.swing.GroupLayout.PREFERRED_SIZE, 601,
javax.swing.GroupLayout.PREFERRED_SIZE)
.addContainerGap(javax.swing.GroupLayout.DEFAULT_SIZE,
Short.MAX_VALUE))

15. );
DialogLayout.setVerticalGroup(
DialogLayout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(DialogLayout.createSequentialGroup()
.addContainerGap()
.addComponent(ColorChooser,
javax.swing.GroupLayout.PREFERRED_SIZE, 316,
javax.swing.GroupLayout.PREFERRED_SIZE)
.addContainerGap(javax.swing.GroupLayout.DEFAULT_SIZE,
Short.MAX_VALUE))
);
setDefaultCloseOperation(javax.swing.WindowConstants.DISPOSE_ON_CLOSE);
setBackground(new java.awt.Color(204, 204, 204));
setResizable(false);
jPanel.setBackground(new java.awt.Color(204, 204, 204));
ComboBox.setModel(new javax.swing.DefaultComboBoxModel(new String[] {
"Server", "Client" }));
ComboBox.setToolTipText("");
ComboBox.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
ComboBoxActionPerformed(evt);
}
});
ButtonOn.setText("On");
ButtonOn.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
ButtonOnActionPerformed(evt);

16. }
});
Send.setText("SEND");
Send.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
SendActionPerformed(evt);
}
});
JUsername.setText("Username");
Username.setText("Server");
javax.swing.GroupLayout jPanelLayout = new
javax.swing.GroupLayout(jPanel);
jPanel.setLayout(jPanelLayout);
jPanelLayout.setHorizontalGroup(
jPanelLayout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(jPanelLayout.createSequentialGroup()
.addContainerGap()
.addGroup(jPanelLayout.createParallelGroup(javax.swing.GroupLayout.Alignment.
LEADING)
.addGroup(jPanelLayout.createSequentialGroup()
.addGroup(jPanelLayout.createParallelGroup(javax.swing.GroupLayout.Alignment.
LEADING, false)
.addGroup(jPanelLayout.createSequentialGroup()
.addComponent(JUsername)
.addGap(18, 18, 18)

17. .addComponent(Username,
javax.swing.GroupLayout.PREFERRED_SIZE, 237,
javax.swing.GroupLayout.PREFERRED_SIZE))
.addComponent(ComboBox, 0,
javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))
.addGap(18, 18, 18)
.addComponent(ButtonOn,
javax.swing.GroupLayout.DEFAULT_SIZE, 99, Short.MAX_VALUE))
.addComponent(ListChat,
javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE,
Short.MAX_VALUE)
.addGroup(jPanelLayout.createSequentialGroup()
.addComponent(TextChat,
javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE,
Short.MAX_VALUE)
.addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
.addComponent(Send,
javax.swing.GroupLayout.PREFERRED_SIZE, 74,
javax.swing.GroupLayout.PREFERRED_SIZE)))
.addContainerGap())
);
jPanelLayout.setVerticalGroup(
jPanelLayout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addGroup(jPanelLayout.createSequentialGroup()
.addGap(18, 18, 18)
.addGroup(jPanelLayout.createParallelGroup(javax.swing.GroupLayout.Alignment.
BASELINE)
.addComponent(ComboBox,
javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE,
javax.swing.GroupLayout.PREFERRED_SIZE)
.addComponent(ButtonOn))
.addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)
.addGroup(jPanelLayout.createParallelGroup(javax.swing.GroupLayout.Alignment.
BASELINE)

18. .addComponent(JUsername)
.addComponent(Username,
javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE,
javax.swing.GroupLayout.PREFERRED_SIZE))
.addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
.addComponent(ListChat,
javax.swing.GroupLayout.PREFERRED_SIZE, 179,
javax.swing.GroupLayout.PREFERRED_SIZE)
.addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
.addGroup(jPanelLayout.createParallelGroup(javax.swing.GroupLayout.Alignment.
LEADING, false)
.addComponent(TextChat,
javax.swing.GroupLayout.PREFERRED_SIZE, 58,
javax.swing.GroupLayout.PREFERRED_SIZE)
.addComponent(Send, javax.swing.GroupLayout.DEFAULT_SIZE,
javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))
.addContainerGap(javax.swing.GroupLayout.DEFAULT_SIZE,
Short.MAX_VALUE))
);
File.setText("File");
BackgroundColor.setText("Background Color");
BackgroundColor.addActionListener(new java.awt.event.ActionListener()
{
public void actionPerformed(java.awt.event.ActionEvent evt) {
BackgroundColorActionPerformed(evt);
}
});
File.add(BackgroundColor);
Exit.setAccelerator(javax.swing.KeyStroke.getKeyStroke(java.awt.event.KeyEven
t.VK_W, java.awt.event.InputEvent.CTRL_MASK));

19. Exit.setText("Exit");
Exit.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
ExitActionPerformed(evt);
}
});
File.add(Exit);
jMenuBar1.add(File);
Help.setText("Help");
About.setText("About");
About.addActionListener(new java.awt.event.ActionListener() {
public void actionPerformed(java.awt.event.ActionEvent evt) {
AboutActionPerformed(evt);
}
});
Help.add(About);
jMenuBar1.add(Help);
setJMenuBar(jMenuBar1);
javax.swing.GroupLayout layout = new
javax.swing.GroupLayout(getContentPane());
getContentPane().setLayout(layout);
layout.setHorizontalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addComponent(jPanel, javax.swing.GroupLayout.DEFAULT_SIZE,
javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)

20. );
layout.setVerticalGroup(
layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
.addComponent(jPanel, javax.swing.GroupLayout.Alignment.TRAILING,
javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE,
Short.MAX_VALUE)
);
pack();
}// </editor-fold>
private void AboutActionPerformed(java.awt.event.ActionEvent evt) {
About a = new About();
a.setVisible(true);// TODO add your handling code here:
}
private void SendActionPerformed(java.awt.event.ActionEvent evt) {
getSend();// TODO add your handling code here:
}
private void ButtonOnActionPerformed(java.awt.event.ActionEvent evt) {
getButtonOn();
// TODO add your handling code here:
}
private void ComboBoxActionPerformed(java.awt.event.ActionEvent evt) {
getComboBox();
}
private void ExitActionPerformed(java.awt.event.ActionEvent evt) {
getExit();// TODO add your handling code here:

21. }
private void BackgroundColorActionPerformed(java.awt.event.ActionEvent
evt) {
getBackgroundColor();// TODO add your handling code here:
}
/**
* @param args the command line arguments
*/
public static void main(String [] args) {
/* Set the Nimbus look and feel */
//<editor-fold defaultstate="collapsed" desc=" Look and feel setting
code (optional) ">
/* If Nimbus (introduced in Java SE 6) is not available, stay with
the default look and feel.
* For details see
http://download.oracle.com/javase/tutorial/uiswing/lookandfeel/plaf.html
*/
try {
for (javax.swing.UIManager.LookAndFeelInfo info :
javax.swing.UIManager.getInstalledLookAndFeels()) {
if ("Nimbus".equals(info.getName())) {
javax.swing.UIManager.setLookAndFeel(info.getClassName());
break;
}
}
} catch (ClassNotFoundException ex) {
java.util.logging.Logger.getLogger(Server.class.getName()).log(java.util.logg
ing.Level.SEVERE, null, ex);
} catch (InstantiationException ex) {

22. java.util.logging.Logger.getLogger(Server.class.getName()).log(java.util.logg
ing.Level.SEVERE, null, ex);
} catch (IllegalAccessException ex) {
java.util.logging.Logger.getLogger(Server.class.getName()).log(java.util.logg
ing.Level.SEVERE, null, ex);
} catch (javax.swing.UnsupportedLookAndFeelException ex) {
java.util.logging.Logger.getLogger(Server.class.getName()).log(java.util.logg
ing.Level.SEVERE, null, ex);
}
//</editor-fold>
/* Create and display the form */
java.awt.EventQueue.invokeLater(new Runnable() {
public void run() {
new Server().setVisible(true);
}
});
}
// Variables declaration - do not modify
private javax.swing.JMenuItem About;
private javax.swing.JMenuItem BackgroundColor;
private javax.swing.JButton ButtonOn;
private javax.swing.JColorChooser ColorChooser;
private javax.swing.JComboBox ComboBox;
private javax.swing.JDialog Dialog;
private javax.swing.JMenuItem Exit;
private javax.swing.JMenu File;
private javax.swing.JMenu Help;
private javax.swing.JLabel JUsername;
private java.awt.List ListChat;

23. private javax.swing.JToggleButton Send;
private java.awt.TextArea TextChat;
private javax.swing.JTextField Username;
private javax.swing.JMenuBar jMenuBar1;
private javax.swing.JPanel jPanel;
// End of variables declaration
@Override
public void run()
{
try {
ListChat.add(Server_Reader.readLine());
} catch (IOException ex) {
Logger.getLogger(Form.class.getName()).log(Level.SEVERE, null,
ex);
}
}
}
Hasil

24. Pembahasan :
Source Code pada program ini hanya bisa dilakukan oleh server dan client, pada pesan dari
client dan server muncul pada layar server dan client.