Thursday, 31 March 2011

Go Back N - Sender & Receiver

1. Go Back N Sender:

import java.io.*;
import java.net.*;
import java.lang.*;
public class gbnsend
{
	 public static void main(String args[])
	 {
		  int serverport=3333;
		 String address="127.0.0.2";
  		try
  		{
   			InetAddress ipaddress=InetAddress.getByName(address);
  			 Socket socket=new Socket(ipaddress,serverport);
   			InputStream sin=socket.getInputStream();
   			OutputStream sout=socket.getOutputStream();
   			DataInputStream in=new DataInputStream(sin);
  			 DataOutputStream out=new DataOutputStream(sout);
   			BufferedReader keyboard=new BufferedReader(new InputStreamReader(System.in));
   			String line=null;
  			 String word []=new String [8];
   			int i;
   			System.out.println("plz input the no of frames to b sent");
  			 int n=Integer.parseInt(keyboard.readLine());
  			 for(i=0;i<n;i++)
			 {
    				word[i]=keyboard.readLine();
   			 }
  			 i=0;
   			while(i<n)
  			 {
    				System.out.println("sending frame "+word[i]);
    				out.writeUTF(word[i]);
    				out.flush();
    				i++;
  			 }
   			try 
  		 	{
    				Thread.sleep(1000);
   			}
   			catch(InterruptedException e)
   			{
    				e.printStackTrace();
   			}
   			line=in.readUTF();
   			System.out.println("nack received for frame "+line);
  			i=Integer.parseInt(line);
   			out.writeUTF(word[i]);
 		 	 System.out.println("retransmitting all frames after "+word[i]);
  			 i++;
  			 while(i<n)
   			 {
    				System.out.println("sending frame "+word[i]);
   				 out.writeUTF(word[i]);
   				 out.flush();
   				 i++;
   			}
  		}
 		 catch(Exception e)
  		{
   			e.printStackTrace();
  		}
 
	 }
}

2. Go Back N Receiver:

import java.net.*;
import java.io.*;
public class gbnreceive
{
 public static void main(String args[])
 {
  int port=3333;
  try
  {
   ServerSocket ss=new ServerSocket(port);
   System.out.println("waiting for user2");
   Socket socket=ss.accept();
   System.out.println("user detected");
   System.out.println();
   InputStream sin=socket.getInputStream();
   OutputStream sout=socket.getOutputStream();
   DataInputStream in=new DataInputStream(sin);
   DataOutputStream out=new DataOutputStream(sout);
   BufferedReader keyboard=new BufferedReader(new InputStreamReader(System.in));
   String line=null;
   String word []=new String [8];
   int i=0;
   while(i<4)
   {
    line=in.readUTF();
    word[i]=line;
    System.out.println("frame "+word[i]+" received successfully");
    i++;
   }
   while(i<8)
   {
    if(i==4)
    {
      System.out.println("frame "+i+" not received");
      i++;
    }
    else
    {
      System.out.println("frame "+i+" discarded");
      i++;
     }
    }
   System.out.println("requesting for retransmaission");
   line=keyboard.readLine();
   out.writeUTF(line);
   out.flush();
   i=4;
   while(i<8)
   {
    line=in.readUTF();
    word[i]=line;
    i++;
   }
   System.out.println("received all retransmitted frames successfully");
  }
  catch(Exception e)
  {
   e.printStackTrace();
  }
  /*finally
  {
   sin.close();
   sout.close();
   in.close();
   out.close();
  }*/
 }
}