C Linux C++/C Dll injection + Code Injection Tutorial - Part Three

Code
#include <stdio.h>

#include <stdlib.h>

#include <arpa/inet.h>

#include <strings.h>

#include <string.h>

#include <unistd.h>

#include <errno.h>



#define DEFAULT_PROTOCOL 0

#define PORT 50000



int main(int argc, char**argv)

{

  int clientfd;

  char recvline[BUFSIZ];

  FILE * fd = NULL;

  struct sockaddr_in servaddr;



  if ( argc != 3 )

  {

    fputs( "Usage error - a.out <IPaddress> <Filename>\n", stderr );

    exit(EXIT_FAILURE);

  }



  if (!(fd = fopen(argv[2], "r")))

  {

    fprintf(stderr, "Could not open %s\n", argv[2]);

    exit(EXIT_FAILURE);

  }



  if ((clientfd = socket(AF_INET, SOCK_STREAM, DEFAULT_PROTOCOL)) < 0)

  {

    perror("socket");

    exit(EXIT_FAILURE);

  }



  bzero(&servaddr, sizeof(servaddr));

  servaddr.sin_family = AF_INET;

  servaddr.sin_port = htons(PORT);



  if ((inet_pton(AF_INET, argv[1], &servaddr.sin_addr.s_addr)) <= 0)

  {

    fputs( "Conversion error!\n", stderr );

    exit(EXIT_FAILURE);

  }



  if ((connect(clientfd, (const struct sockaddr*)&servaddr, sizeof(servaddr))) < 0)

  {

    perror("connect");

    exit(EXIT_FAILURE);

  }



  while ( write(clientfd, recvline, fread(recvline, sizeof(char), BUFSIZ, fd)) )

  {}



  fclose(fd);

  close(clientfd);

  exit(EXIT_SUCCESS);

}