Stopandwaitprotocol.c

#include<conio.h>
#include<dos.h>
#include<stdio.h>
#include<stdlib.h>
#define TIMEOUT 5
#define MAX_SEQ 1
#define TOT_PACKETS 8
#define inc(k) if(k<MAX_SEQ) k++; else k=0;
typedef struct
{
	int data;
}packet;
typedef struct
{
	int kind;
	int seq;
	int ack;
	packet info;
	int err;
}frame;
frame DATA;
typedef enum{frame_arrival,err,timeout,no_event} event_type;
void from_network_layer(packet *);
void to_network_layer(packet *);
void to_physical_layer(frame *);
void from_physical_layer(frame *);
void wait_for_event_sender(event_type *);
void wait_for_event_reciever(event_type *);
void reciever();
void sender();
main()
{
	int DISCONNECT=0;
	rand();
	while(!DISCONNECT)
	{
		sender();
		//delay(40000);
   		reciever();
 	}
 	return 0;
 	getch();
}
void sender()
{
	char turn; 
	static int frame_to_send=0;
 	static frame s;
 	packet buffer;
 	event_type event;
 	static int flag=0;
 	if(flag==0)
 	{
  		from_network_layer(&buffer);
  		s.info = buffer;
  		s.seq = frame_to_send;
  		printf("SENDER :  Info = %d    Seq No = %d     ",s.info,s.seq);
  		turn = 'r';
  		to_physical_layer(&s);
  		flag = 1;
 	}
 	wait_for_event_sender(&event);
 	if(turn=='s')
 	{
   		if(event==frame_arrival)
    	{
      		from_network_layer(&buffer);
      		inc(frame_to_send);
      		s.info = buffer;
      		s.seq = frame_to_send;
      		printf("SENDER :  Info = %d    Seq No = %d     ",s.info,s.seq);
      		turn = 'r';
      		to_physical_layer(&s);
    	}
   		if(event==timeout)
    	{
      		printf("SENDER : Resending Frame             ");
      		turn = 'r';
      		to_physical_layer(&s);
    	}
  	}
}
void reciever()
{
	char turn; 
	static int frame_expected=0;
 	frame r,s;
 	event_type event;
 	wait_for_event_reciever(&event);
 	if(turn=='r')
  	{
   		if(event==frame_arrival)
    	{
     		from_physical_layer(&r);
     		if(r.seq==frame_expected)
      		{
       			to_network_layer(&r.info);
       			inc(frame_expected);
      		}
     		else
       			printf("RECIEVER : Acknowledgement Resent\n");
     		turn = 's';
     		to_physical_layer(&s);
    	}
   		if(event==err)
    	{
    		printf("RECIEVER : Garbled Frame\n");
      		turn = 's';     //if frame not recieved
    	}                 //sender shold send it again
  	}
}
void from_network_layer(packet *buffer)
{
	int i=1;
	(*buffer).data = i;
   	i++;
}
void to_physical_layer(frame *s)
{                     // 0 means error
	s->err = rand();  //non zero means no error
 	DATA = *s;           //probability of error = 1/4
}
void to_network_layer(packet *buffer)
{
	int i=1;
	int DISCONNECT=0;
	printf("RECIEVER :Packet %d recieved , Ack Sent\n",(*buffer).data);
	if(i>TOT_PACKETS)          //if all packets recieved then disconnect
	{
		DISCONNECT = 1;
   		printf("\nDISCONNECTED");
  	}
}
void from_physical_layer(frame *buffer)
{
	*buffer = DATA;
}
void wait_for_event_sender(event_type * e)
{
	char turn;
	static int timer=0;
	if(turn=='s')
  	{
   		timer++;
   		if(timer==TIMEOUT)
    	{
     		*e = timeout;
     		printf("SENDER : Ack not recieved=> TIMEOUT\n");
     		timer = 0;
     		return;
    	}
   		if(DATA.err==0)
     		*e = err;
   		else
    	{
     		timer = 0;
     		*e = frame_arrival;
    	}
  	}
}
void wait_for_event_reciever(event_type * e)
{
	char turn;
	if(turn=='r')
  	{
   		if(DATA.err==0)
     		*e = err;
   		else
     		*e = frame_arrival;
  	}
}