Client Go Back N

#include <arpa/inet.h>
#include <stdio.h>
#include <string.h>
#include <stdbool.h>
#include <sys/socket.h>
#include <unistd.h>
#define PORT 8080

void transfer(int sock){

      int i,e=0;
     while(read(sock,&i,sizeof(i))!=0){
     if(e==i){
     printf("Frame %d recived\t",e);
     e++;
     i++;
     write(sock,&i,sizeof(i));
     printf("Ack %d\n",i);
     }
      }
}

int main(int argc, char const* argv[])
{
    int sock = 0, valread, client_fd,n;
    struct sockaddr_in serv_addr;
    char str[5];
    char buffer[1024] = { 0 };
    if ((sock = socket(AF_INET, SOCK_STREAM, 0)) < 0) {
        printf("\n Socket creation error \n");
        return -1;
    }

    serv_addr.sin_family = AF_INET;
    serv_addr.sin_port = htons(PORT);
    if (inet_pton(AF_INET, "127.0.0.1", &serv_addr.sin_addr)
        <= 0) {
        printf(
            "\nInvalid address/ Address not supported \n");
        return -1;
    }
    if ((client_fd
        = connect(sock, (struct sockaddr*)&serv_addr,
                sizeof(serv_addr)))
        < 0) {
        printf("\nConnection Failed \n");
        return -1;
    }
        transfer(sock);
    close(client_fd);
    return 0;
}