BroadCasting Example using UDP

In this example the Server broadcasts messages to all the connected clients.

Server.java

import javax.swing.*;
import java.awt.*;
import java.awt.event.KeyAdapter;
import java.awt.event.KeyEvent;
import java.net.*;
import java.util.*;
import java.io.*;
public class Server extends JFrame{
JTextArea jtxt ;
JTextField jfld ;
JPanel jp ;
JScrollPane jsp ;

ArrayList clientDtls ;
DatagramPacket dp ;
DatagramSocket ds ;
ReceiveClients clientThread ;

String message ;

private Runnable runnable = new Runnable(){
public void run() {
clientThread.stop() ;
clientDtls.clear() ;
if(! ds.isClosed()) ds.close() ;
System.out.println("\n\nServer shutdown gracefully.......\n\n") ;
}
};

public Server(){
setServer() ;

clientDtls = new ArrayList() ;
clientDtls.ensureCapacity(20) ;

clientThread = new ReceiveClients(clientDtls,ds) ;

initGUI() ;
}

private void initGUI(){
this.setVisible(true) ;
this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE) ;
this.setTitle("SERVER>>>>>>") ;
this.setLocation(200,200) ;

jtxt = new JTextArea(30,20) ;
jfld = new JTextField(20) ;
jp = new JPanel(true) ;
jsp = new JScrollPane(jtxt) ;

jfld.addKeyListener(new KeyAdapter(){
public void keyTyped(KeyEvent ke){
if(ke.getKeyChar() == '\n'){
message = jfld.getText() ;

jfld.setText("") ;
jfld.setEditable(false) ;
if(! message.equals(""))
sendPackets() ;
jfld.setEditable(true) ;
jtxt.append(message+"\n") ;
}
}
}
);

jp.setLayout(new BoxLayout(jp,BoxLayout.Y_AXIS)) ;
jp.add(jsp) ;
jp.add(jfld) ;

jtxt.setEditable(false) ;
jtxt.setFocusable(false) ;

this.getContentPane().add(jp) ;
this.pack() ;
}

public void setServer(){
try {
ds = new DatagramSocket(2000) ;
dp = new DatagramPacket(new byte[256],256) ;
} catch (SocketException e) {
e.printStackTrace();
}
Runtime.getRuntime().addShutdownHook(new Thread(runnable)) ;
}

private void sendPackets(){
int size = clientDtls.size() ;
ClientDtls cd ;
int i = 0 ;
while(i cd = clientDtls.get(i) ;

dp.setAddress(cd.getAddress()) ;
dp.setPort(cd.getPort()) ;
dp.setData(message.getBytes()) ;
dp.setLength(message.length()) ;

try {
ds.send(dp) ;
} catch (IOException e) {
e.printStackTrace();
i++ ;
continue ;
}

i++ ;
}
}

public static void main(String[] args){
Server server = new Server() ;
}
}

class ReceiveClients implements Runnable{
private volatile boolean flag ;
private ArrayList clientDtls ;
private DatagramSocket ds ;
private DatagramPacket input ;

public ReceiveClients(ArrayList ref,DatagramSocket ds){
clientDtls = ref ;
this.ds = ds ;
flag = true ;

input = new DatagramPacket(new byte[256],256) ;

Thread t = new Thread(this,"Receive_Clients") ;

t.start() ;
}
public void run() {
while(flag){
try {
ds.receive(input) ;

String request = new String(input.getData(),0,input.getLength(),"ASCII") ;
request = request.trim() ;

InetAddress ia = input.getAddress() ;
int port = input.getPort() ;

ClientDtls cd = new ClientDtls(ia,port) ;


if(request.equals("CONNECT")){
//if(! clientDtls.contains(sa))
clientDtls.add(cd) ;
}
else if(request.equals("RELEASE")){
clientDtls.remove(cd) ;
}
}catch(SocketException se){
System.out.println("Trying to close the server.....") ;
stop() ;
return ;
}
catch (IOException e) {
e.printStackTrace();
continue ;
}
}
}
public void stop(){
flag = false ;
}
}
class ClientDtls{
private InetAddress address ;
private int port ;
public ClientDtls(InetAddress address,int port){
this.address = address ;
this.port = port ;
}
public boolean equals(ClientDtls cd){
if(cd.getAddress().equals(address)){
if(cd.getPort() == port)
return true ;
}
return false ;
}
public int getPort(){
return port ;
}
public InetAddress getAddress(){
return address ;
}
}




Client.java


import javax.swing.* ;

import java.net.*;
import java.io.*;
import java.awt.*;
import java.awt.event.KeyAdapter;
import java.awt.event.KeyEvent;
public class Client extends JFrame{
JTextArea jtxt ;
JPanel jp ;
JScrollPane jsp ;

DatagramPacket dp ;
DatagramSocket ds ;

private Runnable run = new Runnable(){
public void run() {
if(! ds.isClosed()) ds.close() ;
releaseClient() ;
System.out.println("\nSystem shutdown gracefully......\n\n") ;
}
};
public Client(){
startClient() ;
initGUI() ;
}
private void initGUI(){
this.setVisible(true) ;
this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE) ;
this.setTitle("CLIENT>>>>>>") ;
this.setLocation(300,200) ;

jtxt = new JTextArea(30,20) ;
jp = new JPanel(true) ;
jsp = new JScrollPane(jtxt) ;


jp.setLayout(new BoxLayout(jp,BoxLayout.Y_AXIS)) ;
jp.add(jsp) ;

jtxt.setEditable(false) ;
jtxt.setFocusable(false) ;

this.getContentPane().add(jp) ;
this.pack() ;
}
private void startClient(){
try {
ds = new DatagramSocket() ;
} catch (SocketException e) {
e.printStackTrace();
}
String connect = "CONNECT" ;

dp = new DatagramPacket(new byte[256],256) ;

dp.setData(connect.getBytes()) ;
dp.setLength(connect.length()) ;

try {
dp.setAddress(InetAddress.getLocalHost()) ;
} catch (UnknownHostException e) {
e.printStackTrace();
}

dp.setPort(2000) ;

try {
ds.send(dp) ;
} catch (IOException e) {
e.printStackTrace();
}

Runtime.getRuntime().addShutdownHook(new Thread(run)) ;

}
private void releaseClient(){
String message = "RELEASE" ;

dp.setData(message.getBytes()) ;
dp.setLength(message.length()) ;

try {
ds.send(dp) ;
} catch (IOException e) {
e.printStackTrace();
}
}
private void writeMessage(){
String message = "" ;
try {
message = new String(dp.getData(),0,dp.getLength(),"ASCII") ;
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
}
jtxt.append(message+"\n") ;
}
public void receiveClient(){
while(true){
dp.setData(new byte[256]) ;
dp.setLength(256) ;

try {
ds.receive(dp) ;
writeMessage() ;
} catch (IOException e) {
e.printStackTrace();
}
}

}

public static void main(String[] args){
Client client = new Client() ;
client.receiveClient() ;
}
}