email verification:

public class Connect {
    private String USERNAME = "java";
    private String PASSWORD = "java";
    private int PORT = 9090;
    private String HOSTNAME = "localhost";

    public String getUsername(){
        return this.USERNAME;
    }

    public String getPassword(){

        return this.PASSWORD;
    }

    public int getPort(){
        return this.PORT;
    }

    public String gethostName(){
        return this.HOSTNAME;
    }
}


import java.io.*;
import java.io.net.*;
public class Client {
    private final String FILENAME = null;
    Connect c = new Connect();
    Socket socket;
    BufferedReader read;
    PrintWriter output;

    public void startClient() throws UnknownHostException, IOException{
        //Create socket connection
        socket = new Socket(c.gethostName(), c.getPort());

        //create printwriter for sending login to server
        output = new PrintWriter(new OutputStreamWriter(socket.getOutputStream()));

        //prompt for user name
        String username = JOptionPane.showInputDialog(null, "Enter User Name:");

        //send user name to server
        output.println(username);

        //prompt for password
        String password = JOptionPane.showInputDialog(null, "Enter Password");

        //send password to server
        output.println(password);
        output.flush();

        //create Buffered reader for reading response from server
        read = new BufferedReader(new InputStreamReader(socket.getInputStream()));

        //read response from server
        String response = read.readLine();
        System.out.println("This is the response: " + response);

        //display response
        JOptionPane.showMessageDialog(null, response);
    }

    public void fileInfo(){

    }

    public static void main(String args[]){
        Client client = new Client();
        try {
            client.startClient();
        } catch (UnknownHostException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
}

import java.io.*;
import java.io.net.*;
public class Server {
    private int currentTot;
    ServerSocket serversocket;
    Socket client;
    int bytesRead;
    Connect c = new Connect();
    BufferedReader input;
    PrintWriter output;

    public void start() throws IOException{
        System.out.println("Connection Starting on port:" + c.getPort());
        //make connection to client on port specified
        serversocket = new ServerSocket(c.getPort());

        //accept connection from client
        client = serversocket.accept();

        System.out.println("Waiting for connection from client");

        try {
            logInfo();
        } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

    public void logInfo() throws Exception{
        //open buffered reader for reading data from client
        input = new BufferedReader(new InputStreamReader(client.getInputStream()));

        String username = input.readLine();
        System.out.println("SERVER SIDE" + username);
        String password = input.readLine();
        System.out.println("SERVER SIDE" + password);

        //open printwriter for writing data to client
        output = new PrintWriter(new OutputStreamWriter(client.getOutputStream()));

        if(username.equals(c.getUsername()) &&password.equals(c.getPassword())){
            output.println("Welcome, " + username);
        }else{
            output.println("Login Failed");
        }
		output.flush();
		output.close();
    }
    public static void main(String[] args){
        Server server = new Server();
        try {
            server.start();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
}






Broadcast server program

import java.net.*;
import java.io.*;
public class BroadcastServer
{
	public static void main(String args[]) throws SocketException, IOException
	{
		DatagramSocket aSocket = new DatagramSocket(2000);
		try
		{
			byte[] buffer = new byte[1000];
			DatagramPacket request = new DatagramPacket(buffer,buffer.length);
			aSocket.receive(request);
			System.out.println("Client1 connected..");
			int port1=request.getPort();
			aSocket.receive(request);
			System.out.println("Client2 connected..");
			int port2=request.getPort();
			InetAddress addr = InetAddress.getLocalHost();
			while(true)
			{
				System.out.println("Enter Message to Broadcast: ");
				BufferedReader bufferRead = new BufferedReader(new InputStreamReader(System.in));
			    String str = bufferRead.readLine();
				DatagramPacket client1 = new DatagramPacket(str.getBytes(), str.length(), addr,port1);
				DatagramPacket client2 = new DatagramPacket(str.getBytes(), str.length(), addr,port2);
				aSocket.send(client1);
				aSocket.send(client2);
			}
		}
		finally
		{
			if (aSocket != null)
				aSocket.close();
		}
	}
}

  BROADCAST CLIENT1 PROGRAM
import java.net.*;
import java.io.*;
public class BroadcastClient1
{
	public static void main(String args[]) throws SocketException, IOException
	{
		DatagramSocket aSocket = new DatagramSocket();
		try
		{	while(true)
			{
				String m = "Hello Server";
				InetAddress aHost = InetAddress.getLocalHost();
				DatagramPacket request = new DatagramPacket(m.getBytes(), m.length(), aHost, 2000);
				aSocket.send(request);
				byte[] buffer = new byte[1000];
				DatagramPacket reply = new DatagramPacket(buffer, buffer.length);
				aSocket.receive(reply);
				System.out.println("Broadcast message from server: " + new String(reply.getData()).trim());
			}
		}
		finally
		{
			if (aSocket != null)
				aSocket.close();
		}
	}
}

BROADCAST CLIENT2

import java.net.*;
import java.io.*;
public class BroadcastClient2
{
	public static void main(String args[]) throws SocketException, IOException
	{
		DatagramSocket aSocket = new DatagramSocket();
		try
		{
			while(true)
			{
				String m = "Hello Server";
				InetAddress aHost = InetAddress.getLocalHost();
				DatagramPacket request = new DatagramPacket(m.getBytes(), m.length(), aHost, 2000);
				aSocket.send(request);
				byte[] buffer = new byte[1000];
				DatagramPacket reply = new DatagramPacket(buffer, buffer.length);
				aSocket.receive(reply);
				System.out.println("Broadcast message from server: " + new String(reply.getData()).trim());
			}
		}
		finally
		{
			if (aSocket != null)
				aSocket.close();
		}
	}
}


UDP Date Server Program import java.net.*; import java.io.*; import java.util.*;

public class UDPDateServer {

public static void main(String[] args) throws Exception{

DatagramSocket ss=new DatagramSocket(1234);

while(true){

System.out.println("Server is up....");

byte[] rd=new byte[100]; byte[] sd=new byte[100];

DatagramPacket rp=new DatagramPacket(rd,rd.length);

ss.receive(rp);

InetAddress ip= rp.getAddress();

int port=rp.getPort();

Date d=new Date();   // getting system time

String time= d + "";  // converting it to String

sd=time.getBytes();   // converting that String to byte

DatagramPacket sp=new DatagramPacket(sd,sd.length,ip,port);

ss.send(sp);

rp=null;

System.out.println("Done !! ");
 }
 }
 }

------------------------

UDP Date Client Program

import java.net.*; import java.io.*;

public class UDPDateClient {

public static void main(String[] args) throws Exception{

    System.out.println("Server Time >>>>");

    DatagramSocket cs=new DatagramSocket();

    InetAddress ip=InetAddress.getByName("localhost");

    byte[] rd=new byte[100];     byte[] sd=new byte[100];

    DatagramPacket sp=new DatagramPacket(sd,sd.length,ip,1234);

    DatagramPacket rp=new DatagramPacket(rd,rd.length);

    cs.send(sp);

    cs.receive(rp);

    String time=new String(rp.getData());

    System.out.println(time);

    cs.close();

}

}




Cipher client-1

import java.io.*;
import java.net.*;

public class CipherClient {

	public static void main(String s[]) {
		String hostName = "localhost"; // "192.168.3.107" ;//mb327scs037
		if ( s.length > 0 ) hostName = s[0] ;
		PrintWriter networkOutput = null;
		BufferedReader networkInput = null ;
		try{
			Socket socket= new Socket( hostName , 3000 );
			networkInput = new BufferedReader ( new InputStreamReader( socket.getInputStream()));
			networkOutput = new PrintWriter ( socket.getOutputStream() );
			BufferedReader input = new BufferedReader ( new InputStreamReader ( System.in ) );
			System.out.println("Connected to Echo Server ...");
				String echoString = input.readLine();
				networkOutput.println( echoString );
				networkOutput.flush();
				System.out.println( networkInput.readLine());

		}
		catch(UnknownHostException e ) {
			System.err.println( e );
		}
		catch(IOException e ) {
			System.err.println( e );
		}
		finally {
		 try{
			if ( networkInput != null ) networkInput.close();
			if( networkOutput != null ) networkOutput.close();
		 }
		 catch(IOException e ) { }
		}

Cipher server

import java.io.*;
import java.net.*;

public class CipherServer {

	public static void main(String s[]) {
		String hostName = "localhost"; //"192.168.3.107" ;//mb327scs037
		if ( s.length > 0 ) hostName = s[0] ;

		try{
			ServerSocket server= new ServerSocket( 3000 );
			while( true ) {
				Socket connection = null;
				try{
					connection = server.accept();
					ProcessRequest thread = new ProcessRequest( connection );
					thread.start();
				}
				catch(IOException e ) {
					System.err.println( e );
				}

			}
		}
		catch(IOException e ) {
			System.err.println( e );
		}

	}
}


class ProcessRequest extends Thread {
	  Socket connection;
	 ProcessRequest( Socket connection ) {
		this.connection = connection;
	}
	public void run() {
		PrintWriter networkOutput = null;
		BufferedReader networkInput = null ;
		try{
			networkInput = new BufferedReader ( new InputStreamReader( connection.getInputStream()));
			networkOutput = new PrintWriter ( connection.getOutputStream() );
			String request = networkInput.readLine();
			System.out.println( request );
			byte byteArray[] = request.getBytes();
			for( int i = 0 ; i < byteArray.length ; i++ )
				byteArray[i] += 2;
			String response = new String ( byteArray );
			networkOutput.println( response );
			networkOutput.flush();
		}
		catch(IOException e ) {
			System.err.println( e );
		}
		 finally {
			try {
				connection.close();
			}
			catch(IOException e) { }
		}
	}

}