The document describes a network programming report on a Java chat application. It includes the code for a Server class that implements a threaded server to handle multiple client connections simultaneously. The server opens a port to listen for clients and spins up a new thread for each accepted connection. It then reads and writes data between the server and client over buffered input/output streams. The report notes issues with messages from one client not being visible to others and connection errors that can occur between the client and server.

1. LAPORAN
NETWORK PROGRAMING
Nama : Wahyu Septiansyah
Kelas : TIF 2A
Nim : 201913046
/*
* 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;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.net.ServerSocket;
import java.net.Socket;
import java.net.UnknownHostException;
import java.text.Normalizer.Form;
import java.util.Scanner;
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;
/**
* Creates new form Server
*/
public Server() {
super("www.mhdsyarif.com"); //SetTitle

2. 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");
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);
// }

3. // Server_Reader = new BufferedReader(new
InputStreamReader(client.getInputStream()));
// Server_Writer = new BufferedWriter(new
OutputStreamWriter(client.getOutputStream()));
// } catch (IOException ex) {
// System.out.println("Read Failed");
// System.exit(-1);
// }
final int PORT = 8080;
try {
server = new ServerSocket(PORT);
} catch (IOException ex) {
Logger.getLogger(Server.class.getName()).log(Level.SEVERE, null,
ex);
}
System.out.println("Server started...");
System.out.println("Wating for clients...");
while (true) {
try {
client = server.accept();
} catch (IOException ex) {
Logger.getLogger(Server.class.getName()).log(Level.SEVERE,
null, ex);
}
Thread t = new Thread() {
public void run() {
try {
Server_Reader = new BufferedReader(new
InputStreamReader(client.getInputStream()));
} catch (IOException ex) {
Logger.getLogger(Server.class.getName()).log(Level.SEVERE, null, ex);
}
try {
Server_Writer = new BufferedWriter (new
OutputStreamWriter(client.getOutputStream()));
} catch (IOException ex) {
Logger.getLogger(Server.class.getName()).log(Level.SEVERE, null, ex);
}
try (
PrintWriter out = new
PrintWriter(client.getOutputStream(), true);
Scanner in = new Scanner(client.getInputStream());
) {
while (in.hasNextLine()) {
String input = in.nextLine();
if (input.equalsIgnoreCase("exit")) {
break;
}

4. System.out.println("Received radius from client:
" + input);
// double radius = Double.valueOf(input);
// double area = Math.PI* radius *radius ;
// out.println(area);
}
} catch (IOException e) { }
}
};
t.start();
}
}
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);
}
}
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();

5. 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);
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();
} 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);

6. }
//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")
// <editor-fold defaultstate="collapsed" desc="Generated Code">//GEN-
BEGIN:initComponents
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))
);
DialogLayout.setVerticalGroup(
DialogLayout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)

7. .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);
}
});
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()

8. .addGroup(jPanelLayout.createParallelGroup(javax.swing.GroupLayout.Alignment.
LEADING, false)
.addGroup(jPanelLayout.createSequentialGroup()
.addComponent(JUsername)
.addGap(18, 18, 18)
.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)
.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)

9. .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));
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)

10. .addComponent(jPanel, javax.swing.GroupLayout.DEFAULT_SIZE,
javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
);
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>//GEN-END:initComponents
private void AboutActionPerformed(java.awt.event.ActionEvent evt) {//GEN-
FIRST:event_AboutActionPerformed
About a = new About();
a.setVisible(true);// TODO add your handling code here:
}//GEN-LAST:event_AboutActionPerformed
private void SendActionPerformed(java.awt.event.ActionEvent evt) {//GEN-
FIRST:event_SendActionPerformed
getSend();// TODO add your handling code here:
}//GEN-LAST:event_SendActionPerformed
private void ButtonOnActionPerformed(java.awt.event.ActionEvent evt)
{//GEN-FIRST:event_ButtonOnActionPerformed
getButtonOn();
// TODO add your handling code here:
}//GEN-LAST:event_ButtonOnActionPerformed
private void ComboBoxActionPerformed(java.awt.event.ActionEvent evt)
{//GEN-FIRST:event_ComboBoxActionPerformed
getComboBox();
}//GEN-LAST:event_ComboBoxActionPerformed
private void ExitActionPerformed(java.awt.event.ActionEvent evt) {//GEN-
FIRST:event_ExitActionPerformed
getExit();// TODO add your handling code here:
}//GEN-LAST:event_ExitActionPerformed
private void BackgroundColorActionPerformed(java.awt.event.ActionEvent
evt) {//GEN-FIRST:event_BackgroundColorActionPerformed
getBackgroundColor();// TODO add your handling code here:
}//GEN-LAST:event_BackgroundColorActionPerformed
/**
* @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

11. */
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) {
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//GEN-BEGIN:variables
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;
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//GEN-END:variables
@Override
public void run()
{

12. try {
ListChat.add(Server_Reader.readLine());
} catch (IOException ex) {
Logger.getLogger(Form.class.getName()).log(Level.SEVERE, null,
ex);
}
}
}
Keterangan:
Masalah dari aplikasi chatting ini adalah apabila client 1 mengirim pesan ke server maka client 2
dan client yang lain nya tidak bisa melihat isi chat tersebut. Selain itu apabila, apabila client
mengirim pesan ke server. Biasa nya terjadi coonection refused : connect yang terjadi
dikaernakan jaringan dan juga server yang tidak menerima client.