Learning Java Program

import java.io.*;
import java.net.*;
class slidingSender
{
    public void process()
    {
        try
        {
            ServerSocket server= new ServerSocket(2500);
            Socket client = server.accept();
            BufferedReader user=new BufferedReader(new InputStreamReader(System.in));
            BufferedReader br=new BufferedReader(new InputStreamReader(client.getInputStream()));
            PrintWriter pr=new PrintWriter(client.getOutputStream(),true);
            String buf[]=new String[8];
            int index=0,sws=8,rws;
            String ch;
            do
            {
                System.out.println("Enter the number of frame send to the receiver:");
                int nf=Integer.parseInt(user.readLine());
                pr.println(nf);
                if(nf<=sws-1)
                {
                    System.out.println("Enter the "+nf+" Message send to the receiver");
                    for(int i=0;i<nf;i++)
                    {
                        buf[i]=user.readLine();
                        pr.println(buf[i]);

                    }
                   
                    sws=sws-nf;
                    int ackno=Integer.parseInt(br.readLine());
                    System.out.println("Acknowledge Received For the Frame"+ackno);
                    sws=sws+nf;

                }
                else
                {
                    System.out.println("SENDER WINDOW SIZE EXCEEDS");
                }
                System.out.println("Do You Want To Continue(y/n)");
                ch=user.readLine();
                pr.println(ch);
            }
            while(ch.equals("y"));
        }
        catch(Exception e){}
    }
    public static void main(String arg[])
    {
        slidingSender s= new slidingSender();
        s.process();
    }

}

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

class slidingReceiver
{
    public void process()
    {
        try
        {
            Socket client = new Socket(InetAddress.getLocalHost(),2500);
            BufferedReader br = new BufferedReader(new InputStreamReader(client.getInputStream()));
            BufferedReader user=new BufferedReader(new InputStreamReader(System.in));
            PrintWriter pr=new PrintWriter(client.getOutputStream(),true);
            int index=0,rws=8;
            String buf[]=new String[8];
            String ch;
            while(true)
            {
                do
                {
                    int nf=Integer.parseInt(br.readLine());
                    if(nf<rws-1)
                    {
                        for(int i=0;i<nf;i++)
                        {
                            buf[index]=br.readLine();
                            System.out.println(index);
                            System.out.println(buf[index]);
                            index=(index +1)%rws;
                            System.out.println(index);
                        }
                        rws = rws - nf;                      
                        System.out.println("Acknowledge Sent To Sender");
                        pr.println(index);
                        rws=rws+nf;
                    }
                    else
                    {
                        break;
                    }
                    ch=br.readLine();
                }
                while(ch.equals("y"));
            }
        }
        catch(Exception e){}
    }
    public static void main(String arg[])
    {
        slidingReceiver r= new slidingReceiver();
        r.process();
    }
}

Enter the number of frame send to the receiver:
3
Enter the 3 Message send to the receiver
hi
good
evening
Acknowledge Received For the Frame3
Do You Want To Continue(y/n)
n

0 

hi 

1 

1 

good 

2 

2 

evening 

3 

Acknowledge Sent To Sender 

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

class MulticastSender implements Runnable
{
    static int port;
    static MulticastSocket ms;
    static String group;
    static int status = 0 ;
    MulticastSender() throws Exception
    {
        port = 5000;
        group = "225.4.5.6";
        ms = new MulticastSocket(4000);
    }
    public void run()
    {
        while(true)
        {
            try
            {
                BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
                byte sbuf[] = new byte[2000];
                sbuf = br.readLine().getBytes();
                DatagramPacket spack = new DatagramPacket(sbuf, sbuf.length,
                                                 InetAddress.getByName(group), port);
                ms.send(spack);                                                
               
            }catch(Exception e){ System.out.println(e);}
        }
    }
    public static void main(String args[]) throws Exception
    {
        MulticastSender sender = new MulticastSender();
        Thread t = new Thread(sender);
               
        ms.joinGroup(InetAddress.getByName(group));
        t.start();
       
        int count =0;
        byte rbuf[] = new byte[1000];
        while(true)
        {
            DatagramPacket rpack =new DatagramPacket(rbuf,rbuf.length);
            ms.receive(rpack);
            String str = new String(rpack.getData(),0,rpack.getLength());
            if(str.equalsIgnoreCase("join"))
            {
                count++;
                System.out.println("Client joined the group");
                System.out.println("\ncurrently " + count + " client/clients is/are in the group");
               
            }
            else if(str.equalsIgnoreCase("leave"))
            {
                count--;
                System.out.println("Client left the group");
                System.out.println("\ncurrently " + count + " client/clients is/are in the group");
                if(count == 0)
                {
                    ms.leaveGroup(InetAddress.getByName(group));
                    ms.close();
                    break;
                }
            }
        }
    }
}

import java.io.*;
import java.net.*;
class MulticastReceiver implements Runnable
{
    static MulticastSocket ms;
    static int port;
    static int status = 0;
    MulticastReceiver() throws Exception
    {
        port = 5000;
        ms= new MulticastSocket(port);
    }
    public void run()
    {
        while(true)
        {
            try
            {
                byte rbuf[] = new byte[2000];
                DatagramPacket  rpack = new DatagramPacket(rbuf,rbuf.length);
                if (status == 1)
                {
                    ms.close();
                    break;
                }
                ms.receive(rpack);
                System.out.println(new String(rpack.getData(),0,rpack.getLength()));
            }catch(Exception e){System.out.println(e);}
        }
    }
   
    public static void main(String args[]) throws Exception
    {
        MulticastReceiver mr =new MulticastReceiver();
        Thread t = new Thread(mr);
       
        String group = "225.4.5.6";
      
        System.out.println("Do you wish to join the group?");
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        if(br.readLine().equalsIgnoreCase("yes"))
        {
            ms.joinGroup(InetAddress.getByName(group));
           
            byte sbuf[] = new byte[2000];
            sbuf = "join".getBytes();
            DatagramPacket spack = new DatagramPacket(sbuf, sbuf.length,InetAddress.getByName("localhost"),4000);
            ms.send(spack);
          
            System.out.println("Joined the group");
            t.start();
            while(true)
            {
                if(br.readLine().equalsIgnoreCase("leave"))
                {
                    status = 1;
                    byte sbuf2[] = new byte[2000];
                    sbuf2 = "leave".getBytes();
                    DatagramPacket spack2 = new DatagramPacket(sbuf2,sbuf2.length,InetAddress.getByName("localhost"),4000);
                    ms.send(spack2);
                    ms.leaveGroup(InetAddress.getByName(group));
                    break;
                }
            }
        }
    }
}

Do you wish to join the group?
yes
Joined the group
hi

Client joined the group

currently 1 client/clients is/are in the group
hi

Client Side Program

import java.io.*;
import java.net.*;
class TCPClient {

  public static void main(String args[]) throws Exception
  {
       String sentence;
       String modifiedSentence;
        BufferedReader inFromUser =
         new BufferedReader(new InputStreamReader(System.in));

      Socket clientSocket = new Socket("127.0.0.1", 6324);

        DataOutputStream outToServer =
          new DataOutputStream(clientSocket.getOutputStream());
   
       BufferedReader inFromServer =
          new BufferedReader(new
            InputStreamReader(clientSocket.getInputStream()));

        sentence = inFromUser.readLine();
        outToServer.writeBytes(sentence + '\n');

        modifiedSentence = inFromServer.readLine();

        System.out.println("FROM SERVER: " + modifiedSentence);

        clientSocket.close();
                 
    }
}

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

class TCPServer {

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

      ServerSocket welcomeSocket = new ServerSocket(6324);
 
      while(true) {
 
            Socket connectionSocket = welcomeSocket.accept();

           BufferedReader inFromClient =
              new BufferedReader(new
              InputStreamReader(connectionSocket.getInputStream()));

          
DataOutputStream  outToClient =
             new DataOutputStream(connectionSocket.getOutputStream());

           clientSentence = inFromClient.readLine();
           System.out.println("FROM client:" + clientSentence); 
           capitalizedSentence = clientSentence.toUpperCase() + '\n';
           outToClient.writeBytes(capitalizedSentence);
        }
    }
}

hi

FROM SERVER: HI

FROM client:hi

hi da