(sender side) Java Program to implement Stop and Wait Protocol while sending a message travelling from sender to receiver (CN)

/*Aim: A Java Program implementing Stop and Wait Protocol while sending a message travelling from sender to receiver. */
/*For complete explanation visit: Prof. Brinda's Blog*/
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.net.Socket;

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",2009);
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();
}
}

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.