go_n_server.c

#include <stdio.h>
#include <stdlib.h>
#include <sys/socket.h>
#include <sys/time.h>
#include <netinet/in.h>
#include <string.h>
#include <unistd.h>
#include <arpa/inet.h>
void main()
{
	int server_sock, acpt_sock, ret_val, i=-1;
	char msg[50] = "Received frame", read_buff[50], write_buff[50];
	fd_set set;
	struct sockaddr_in serv_addr, other_addr;
	struct timeval timeout;
	socklen_t len;
	server_sock = socket(AF_INET, SOCK_STREAM, 0);
	memset(&serv_addr, 0, sizeof(serv_addr));
	memset(&other_addr, 0, sizeof(other_addr));
	serv_addr.sin_family = AF_INET;
	serv_addr.sin_port = htons(7004);
	serv_addr.sin_addr.s_addr = INADDR_ANY;
	if (bind(server_sock, (struct sockaddr *)&serv_addr, sizeof(serv_addr)) == -1)
	{
	printf("Binding failed");
	exit(0);
	}
	printf("\nSender of Go Back N where N = 8\n");
	listen(server_sock, 5);
	len = sizeof(other_addr);
	acpt_sock = accept(server_sock, (struct sockaddr *)&other_addr, &len);
	zero:
		i = i + 1;
		memset(&write_buff, 0, sizeof(write_buff));
		strcpy(write_buff, msg);
		write_buff[strlen(msg)] = i + '0';
		printf("To Receiver -> Frame %d\n", i);
		write(acpt_sock, write_buff, sizeof(write_buff));
		i = i + 1;
		sleep(1);
	one:
		memset(&write_buff, 0, sizeof(write_buff));
		strcpy(write_buff, msg);
		write_buff[strlen(msg)] = i + '0';
		printf("To Receiver -> Frame %d\n", i);
		write(acpt_sock, write_buff, sizeof(write_buff));
		FD_ZERO(&set);
		FD_SET(acpt_sock, &set);
		timeout.tv_sec = 2;
		ret_val = select(acpt_sock + 1, &set, NULL, NULL, &timeout);
		if (ret_val == -1)
			printf("Error in select()");
		else if (ret_val == 0) 
		{
			printf("\n--- Timer Timeout - Packet %d Sent Lost ---\n", i - 1);
			printf("--- Restart Timer - Resending Packets in Go Back N Method ---\n\n");
			i = i - 2;
			goto zero;
		}
		else 
		{
			read(acpt_sock, read_buff, sizeof(read_buff));
			if ((i == 6) || (i == 4) || (i == 1))
			{
			printf("--- From Receiver <- %s -- Cumulative Acknowledgement ---\n",read_buff);
			}
			else
			{
			printf("--- From Receiver <- %s -- Individual Acknowledgement ---\n",read_buff);
			}
			printf("-----------------------------------------------------\n");
			i++;
			if (i > 7)
			exit(0);
			if ((i == 5) || (i == 3)) {
			i--;
			goto zero;
			}
			if ((i < 8) || (i != 5))
			goto one;
		}
		close(acpt_sock);
		close(server_sock);
}