Implementation of Stop and Wait Protocol

AIM

To write a java program to perform sliding window protocol

ALGORITHM:

1.Start the program.

2.Get the frame size from the user

3.To create the frame based on the user request. 4.To send frames to server from the client side.

5.If your frames reach the server it will send ACK signal to client otherwise it will send NACK signal to client.

6.Stop the program

PROGRAM

/SENDER PROGRAM

import java.io.*;

import java.net.*;

public class Sender{

Socket sender;

ObjectOutputStream out;

ObjectInputStream in;

String packet,ack,str, msg;

int n,i=0,sequence=0;

Sender(){}

public void run(){

 try{

 BufferedReader br=new BufferedReader(new InputStreamReader(System.in));

System.out.println("Waiting for Connection....");

 sender = new Socket("localhost",2004);

sequence=0;

out=new ObjectOutputStream(sender.getOutputStream());

out.flush();

 in=new ObjectInputStream(sender.getInputStream());

 str=(String)in.readObject();

 System.out.println("reciver     > "+str);

System.out.println("Enter the data to send....");

packet=br.readLine();

n=packet.length();

do{

try{

 if(i<n){

msg=String.valueOf(sequence);

msg=msg.concat(packet.substring(i,i+1));

}

else if(i==n){

 msg="end";out.writeObject(msg);break;

}

out.writeObject(msg);

sequence=(sequence==0)?1:0;

out.flush();

System.out.println("data sent>"+msg);

ack=(String)in.readObject();

System.out.println("waiting for ack.....\n\n");

if(ack.equals(String.valueOf(sequence))){

i++;

System.out.println("receiver   >  "+" packet recieved\n\n");

}

else{     

System.out.println("Time out resending data....\n\n");

sequence=(sequence==0)?1:0;

}

}catch(Exception e){}

}while(i<n+1);

System.out.println("All data sent. exiting.");

}catch(Exception e){}

finally{

try{

in.close();

out.close();

sender.close();

}

catch(Exception e){}

}

}

public static void main(String args[]){

Sender s=new Sender();

s.run();

}

}

//RECEIVER PROGRAM

import java.io.*;

import java.net.*;

public class Reciever{

ServerSocket reciever;

Socket connection=null;

ObjectOutputStream out;

ObjectInputStream in;

String packet,ack,data="";

int i=0,sequence=0;

Reciever(){}

public void run(){

try{

BufferedReader br=new BufferedReader(new InputStreamReader(System.in));

reciever = new ServerSocket(2004,10);

System.out.println("waiting for connection...");

connection=reciever.accept();

sequence=0;

System.out.println("Connection established   :");

out=new ObjectOutputStream(connection.getOutputStream());

out.flush();

in=new ObjectInputStream(connection.getInputStream());

out.writeObject("connected    .");

do{

try{

packet=(String)in.readObject();

if(Integer.valueOf(packet.substring(0,1))==sequence){

data+=packet.substring(1);

sequence=(sequence==0)?1:0;

System.out.println("\n\nreceiver         >"+packet);

}

else

{

System.out.println("\n\nreceiver         >"+packet +"   duplicate data");

}

if(i<3){

out.writeObject(String.valueOf(sequence));i++;

}

else{

out.writeObject(String.valueOf((sequence+1)%2));

i=0;

}

}

catch(Exception e){}

}while(!packet.equals("end"));

System.out.println("Data recived="+data);

out.writeObject("connection ended    .");

}

catch(Exception e){}

finally{

try{

in.close();

out.close();

reciever.close();

}

catch(Exception e){}

}

}

public static void main(String args[]){

Reciever s=new Reciever();

while(true){

s.run();

}

}

}
OUTPUT:

//SENDER OUTPUT

Waiting for Connection....

reciver > connected     .

Enter the data to send....

myname

data sent>0m

waiting for ack.....

receiver        >   packet recieved

data sent>1y

waiting for ack.....

receiver        >   packet recieved

data sent>0n

waiting for ack.....

receiver        >   packet recieved

data sent>1a

waiting for ack.....

Time out resending data....

data sent>1a

waiting for ack.....

receiver        >   packet recieved

data sent>0m

waiting for ack.....

receiver        >   packet recieved

data sent>1e

waiting for ack.....

receiver        >   packet recieved

All data sent. exiting.

//RECEIVER OUTPUT

waiting for connection...

Connection established  :

receiver        >0m

receiver        >1y

receiver        >0n

receiver        >1a

receiver        >1a   duplicate data

receiver        >0m

receiver        >1e

Data recived=myname

waiting for connection...