StopWait.cpp

/* This code is contributed by Sourajita Dewasi. Stop and Wait Protocol: Send one packet and wait for it's independent acknowledgement before sending
the next packet. If the data packet is lost, the acknowledgement doesn't come, it means the data packet
needs to be retransmitted by the user.Even if the acknowledgement is lost, the sender retransmits the 
data packet. Seeing an already sent data packet, the receiver sends an acknowledgement but silently 
discards the duplicate packet. */

#include <iostream>
using namespace std;

struct Sender{
    int PacketNo;
    int Sent;
    int Acknowledged;
}S[6];

struct Receiver{
    int AcknowledgementNo;
    int Received;
    int AcknowledgementSent;
}R[6];

/* We are assuming the 4th data packet is lost and the acknowledgement of 6 data packet is also lost */
int i=0;

int main() {
    
    //Making the data packets at Sender side from 0 to 5
	for (i=0; i<6; i++){
	    S[i].Sent=0;
	    S[i].Acknowledged=0;
	    S[i].PacketNo=i;
	}
	
	//Making the data packets at Sender side from 1 to 6
	for (i=1; i<=6; i++){
	    R[i].AcknowledgementSent=0;
	    R[i].Received=0;
	    R[i].AcknowledgementNo=i;
	}
	
	int check4=0; int check6=0; //To study the cases of retransmission by manually causing data packet corruption
	
	//Sending and receiving the data packets
	for(i=0; i<6; i++){
	    cout<<"\n\n Next Transmission";
	    cout<<"\n Sending PacketNo "<<i<<" from Sender";
	    S[i].Sent=1;
	    cout<<"\n Propagation Delay";
	    if(i==4 && check4==0){
	        R[i].Received=0;
	        check4=1; i--;
	        cout<<"\n Data PacketNo "<<i<<" not received.";
	    }
	    else{
	        R[i].Received=1;
	        R[i].AcknowledgementSent=1;
	        cout<<"\n Sending AcknowledgementNo "<<i+1<<" to Sender";
	        cout<<"\n Propagation Delay";
	        if(i==5 && check6==0){
	            S[i].Acknowledged=0;
	            check6=1;i--;
	            cout<<"\n Acknowledgement for DataPacketNo"<< i <<" not received";
	        }
	        else{
	            S[i]. Acknowledged=1;
	            cout<<"\n Acknowledgement for PacketNo "<<i<<" Received";
	            
	        }
	        
	}}
	return 0;
}