goback

#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<unistd.h>
#include<sys/types.h>
#include<sys/select.h>
#include<arpa/inet.h>
#include<stdlib.h>
#include<pthread.h>
#define timeoutValue 5
#define packetCount 5
#define windowSize 3

void sendWindowPackets( int *sockfd,struct sockaddr_in addr,int packets[],int windowStart, int windowEnd)
{
char buffer[1024];
while(windowStart<windowEnd)
{
bzero(buffer,1024);
sprintf(buffer," %d", packets[windowStart]);
printf(" Client : Sending packet %s \n", buffer);
sendto(*sockfd,buffer, 1024,0,(struct sockaddr*)&addr, sizeof(addr));
windowStart++;
}
}
void main()
{
char *ip = " 127.0.0.100 ";
int port = 5555;
pthread_t timeoutThread;
int sockfd;
struct sockaddr_in addr;
char buffer[1024];
socklen_t addr_size;
sockfd = socket(AF_INET,SOCK_DGRAM,0);
if(sockfd<0)
{
perror ( " [ -] Socket error " );
exit(1);
}

memset(&addr,'\0', sizeof(addr));
addr.sin_family = AF_INET;
addr.sin_port = htons(port);
addr.sin_addr.s_addr = inet_addr(ip);
int packets[packetCount];
for(int i=0;i<packetCount;++i)
packets[i]=i+1;
int windowStart=0;
int windowEnd=windowStart+windowSize;
int flag=1;
sendWindowPackets(&sockfd,addr,packets,windowStart,windowEnd);
while(windowStart!=windowEnd)
{
bzero(buffer,1024);
addr_size=sizeof(addr);
struct timeval timeout;
timeout.tv_sec=timeoutValue;
timeout.tv_usec= 0;
if(setsockopt(sockfd,SOL_SOCKET,SO_RCVTIMEO,&timeout,sizeof(timeout))<0)
printf(" Error \n");
else
{
bzero(buffer,1024);
addr_size= sizeof(addr);
int rec=recvfrom(sockfd,buffer,1024,0,(struct sockaddr*) &addr, &addr_size);
if(rec<0)
{
printf(" Client : Timeout error! Sending window packets again \n ");
sendWindowPackets(&sockfd,addr,packets,windowStart,windowEnd);
}
else
{
printf(" Client:Received acknowledgement for packet %s \n",buffer);
if(atoi(buffer)!=packets[windowStart]) 
{
printf("Client : Wrong acknowledgement!Sending window packets again \n");
sendWindowPackets(&sockfd,addr,packets, windowStart,windowEnd);
}
else 
{
windowStart++;
if(windowEnd<packetCount)
windowEnd++;
if(windowStart!=windowEnd)
{
bzero(buffer,1024);
if(flag==1)
{
sprintf(buffer,"%d",packets[windowEnd -1]);
printf("Client : Sending packet %s \n" , buffer);
sendto(sockfd,buffer,1024,0,(struct sockaddr*)&addr,sizeof(addr));
}
if(windowEnd==packetCount)
flag=0;
}
}
}
}
sleep(1);
}
}