// Stop and Wait Protocol
// Using Timers to create delays and
Timeout
// Sender
import java.io.*;
import java.net.*;
import java.util.*;
public class Sdr
{
Socket
sender;
ObjectOutputStream
out;
ObjectInputStream
in;
String
pkt, ack="", data="";
int
seq = 0;
boolean
Dup = false;
Sdr()
{
}
public
void run() throws IOException
{
BufferedReader
br = new BufferedReader(new InputStreamReader(System.in));
sender
= new Socket("localhost",1500);
sender.setSoTimeout(5*1000);
seq
= 0;
out
= new ObjectOutputStream(sender.getOutputStream());
in
= new ObjectInputStream(sender.getInputStream());
while(true)
{
try
{
if(Dup)
{
out.writeObject(pkt);
Dup
= false;
}
else
{
System.out.print("\nEnter
the data to send : ");
data
= br.readLine().trim();
pkt
= String.valueOf(seq);
pkt
= pkt.concat(data);
out.writeObject(pkt);
}
out.flush();
try
{
ack
= (String)in.readObject();
if(data.equals("Terminate"))
break;
if(ack.equals(String.valueOf(seq)))
{
System.out.println("ack
received : " + ack);
seq
= (seq==0)?1:0;
}
else
Dup
= true;
}
catch(SocketTimeoutException ste)
{
System.out.println("Ack
timeout. resend data");
Dup
= true;
}
}
catch(Exception
e)
{
}
}
in.close();
out.close();
sender.close();
System.out.println("\nConnection
Terminated.");
}
public static void main(String args[]) throws IOException
{
Sdr s = new Sdr();
s.run();
}
}
// Stop and Wait Protocol
// Reciever
import java.io.*;
import java.net.*;
import java.util.*;
public class Rcr
{
ServerSocket
reciever;
Socket
conc = null;
ObjectOutputStream
out;
ObjectInputStream
in;
String
ack, pkt, data="";
int
seq = 0, delay ;
Random
r = new Random();
Rcr()
{
}
public
void run() throws IOException, InterruptedException
{
BufferedReader br = new BufferedReader(new
InputStreamReader(System.in));
reciever
= new ServerSocket(1500,10);
conc
= reciever.accept();
if(conc!=null)
System.out.println("Connection
established :");
out
= new ObjectOutputStream(conc.getOutputStream());
in
= new ObjectInputStream(conc.getInputStream());
while(true)
{
try
{
pkt
= (String)in.readObject();
ack
= pkt.substring(0,1);
data
= pkt.substring(1);
if(data.equals("Terminate"))
break;
if(Integer.valueOf(ack)
== seq)
{
delay
= r.nextInt(10);
Thread.currentThread().sleep(delay*1000);
System.out.println("\nMsg
received : "+data);
System.out.println("sending
ack " +ack);
out.writeObject(ack);
seq
= (seq==0)?1:0;
}
else
out.writeObject(ack);
out.flush();
}
catch(Exception
e)
{
}
}
in.close();
out.close();
reciever.close();
System.out.println("\nConnection
Terminated.");
}
public static void main(String args[]) throws
IOException, InterruptedException
{
Rcr r = new Rcr();
r.run();
}
}
