MAIN MENU BIODATA ASSIGNMENTS TUTORIALS EMAILS
DISTRIBUTED SYSTEMS(TCT 2034)
ASSIGNMENT 2
(SOCKET PROGRAMMING)
QUESTION:
Modify the earlier program to
allow the client to modify the contents of the file and send the file back to
server for storage. The user can edit the file in a JTextArea, then click a save
changes button to send the file back to server.
Answer:
//Server.java
import java.net.*;
import java.io.*;
public class Server {
private ServerSocket server;
private Socket connection;
private BufferedReader input;
private BufferedWriter output;
//constructor
public Server()
{
//create ServerSocket
try {
server = new ServerSocket(5000, 10);
}
//process problems communicating with server
catch(IOException exception) {
exception.printStackTrace();
System.exit(0);
}
}
//run server
public void runServer()
{
//wait for connection, get streams, read file
try {
//allow server to accept connection
connection = server.accept();
//set up output stream
output = new BufferedWriter(new OutputStreamWriter(
connection.getOutputStream()));
//flush output buffer to send header information
output.flush();
// set up input stream
input = new BufferedReader(new InputStreamReader(
connection.getInputStream()));
//receive file name from client
File file = new File(input.readLine());
String result;
//send file to client
if(file.exists()) {
BufferedReader fileInput = new BufferedReader(
new InputStreamReader(new FileInputStream(file)));
//write first 13 characters
output.write("The file is:\n", 0, 13);
output.flush();
//read first line of file
result = fileInput.readLine();
while(result != null) {
output.write(result + '\n', 0, result.length() + 1);
output.flush();
result = fileInput.readLine();
}
}
//file does not exist
else {
result = file.getName()+"does not exist\n";
output.write(result,0,result.length());
output.flush();
}
//close streams and socket
output.close();
input.close();
connection.close();
}
//process problems communicating with server
catch(IOException ioException){
System.err.println("IOException has occured!");
ioException.printStackTrace();
System.exit(0);
}
} // end method run server
//execute application
public static void main(String args[])
{
Server application=new Server();
application.runServer();
}
}//end class Server
/**Write student information to the file**/
private synchronized static void writeToFile(Student student){
try{
//Append it to "student.dat"
raf.seek(raf.length());
student.writeSti=udent(raf);
//Dispaly data saved
jtaLog.append("The following info saved in the file\n");
jtaLog.append(student.toString());
}
catch(Exception ex){
jtaLog.append(new Date() + ": " + ex);
}
}
//Define a thread to process the client registration
class RegistrationThread extends Thread{
//The socket to serve a client
private Socket socket;
//Buffered reader to get input from the client
private BufferedReader in;
}
public void run(){
String name;
String street;
String city;
try{
//Receive data from the client
name=new String(in.readLine());
street=new String(in.readLine());
city=new String(in.readLine());
//create student instance
Student student=
new Student(name, street, city);
writeToFile(student);
}
catch(IOException ex){
System.out.println(ex);
}
}
//Client.java
import java.awt.*;
import java.net.*;
import java.io.*;
import java.awt.event.*;
//Java extrension packeges
import javax.swing.*;
public class Clientedit extends JFrame implements ActionListener{
private JTextField fileField;
private JTextArea contents;
private JButton jbtSave = new JButton("Save Changes");
private BufferedReader bufferInput;
private BufferedWriter bufferOutput;
private Socket connection;
private JPanel panel;
private JLabel label;
private JScrollPane scroller;
//set up GUI, connect to server, get streams
public Clientedit()
{
//set up GUI
label=new JLabel("Enter file name to retrieve:");
panel=new JPanel();
panel.setLayout(new GridLayout(1,2,0,0));
panel.add(label);
fileField=new JTextField();
fileField.addActionListener(this);
panel.add(fileField);
contents=new JTextArea();
scroller=new JScrollPane(contents);
Container container=getContentPane();
container.setLayout(new BorderLayout());
container.add(panel,BorderLayout.NORTH);
container.add(scroller,BorderLayout.CENTER);
container.add(jbtSave, BorderLayout.SOUTH);
//Register listener
jbtSave.addActionListener(this);container.add(
//connect to server, get streams
try{
//create Socket to make connection to server
connection=new Socket(InetAddress.getLocalHost(),5000);
//set up output stream
bufferOutput=new BufferedWriter(new OutputStreamWriter(
connection.getOutputStream()));
//flush output buffer to send header information
bufferOutput.flush();
//set up input stream
bufferInput=new BufferedReader(new InputStreamReader(
connection.getInputStream()));
}
//process problems communicating with server
catch(IOException ioException){
ioException.printStackTrace();
}
setSize(500,500);
show();
}
//process file name entered by user
public void actionPerformed(ActionEvent event)
{
//display contents of file
try{
String fileName=event.getActionCommand()+"\n";
bufferOutput.write(fileName,0,fileName.length());
bufferOutput.flush();
String output=bufferInput.readLine();
contents.setText(output);
//if file exists, display file contents
if(output.equals("The file is:")){
output=bufferInput.readLine();
while(output!=null){
contents.append(output+"\n");
output=bufferInput.readLine();
}
}
fileField.setEditable(false);
fileField.setBackground(Color.lightGray);
fileField.removeActionListener(this);
//close streams and socket
bufferOutput.close();
bufferInput.close();
connection.close();
}
//end of file
catch(EOFException eofException){
System.out.println("End of file");
}
//process problems communicating with server
catch(IOException ioException){
ioException.printStackTrace();
}
}
//execute application
public static void main(String args[])
{
Client application=new Client();
application.setDefaultCloseOperation(
JFrame.EXIT_ON_CLOSE);
}
}//end class Client
public class RegistrationClient extends JApplet
implements ActionListener{
//Button for registering a student in the file
private JButton jbtRegister = new JButton("Save Changes");
//Create a student information panel
private StudentPanel studentPanel = new StudentPanel();
//Indicate if it runs as applicatiuon
private boolean isStandAlone = false;
//Host name or ip
private String host = "localhost";
public void init(){
//Add the student panel and button to the applet
getContentPane().add(StudentPanel, BorderLayout.CENTER);
getContentPane().add(jbtRegister, BorderLayout.SOUTH);
//Register listenerjbtRegister.addActionListener(this);
}
/**Handle button action*/
public void actionPerformed(ActionEvent e){
if(e.getSour);
//Get text field
Student s = studentPanel.getStudent();
//Get data from text fields and send it to the server
toServer.println(s.getName());
toServer.println(s.getStreet());
toServer.println(s.getCity());
}
catch(ioException ex){
System.err.println(ex);
}
}
}
/**Run the applet as an application */
public static void main(String[] args{
//Create a frame
JFrame frame = new JFrame("Register Student Client");
//Create an instance of the applet
RegistrationClient applet = new RegistrationClient();
applet.isStandAlone = true;
//Get host
if (args.length == 1) applet.host = args[0];
//Add the applet instance to the frame
frame.getContentPane().add(applet, BorderLayout.CENTER);
//Invoke init() and start()
applet.init();
applet.start();
//Display the frame
frame.pack();
frame.setVisible();
}
}
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OUTPUT
.jpg)