#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h>
#include <stdio.h>
#include <errno.h>
#include <string.h>
#include <stdlib.h>
#include <ctype.h>

int main (int argc, char **argv) {

  size_t buflen = 1024;
  char buf[buflen];
  struct sockaddr_in from;
  socklen_t fromlen = sizeof(struct sockaddr_in);
  int flags;

  int rawsock;
  int bytesread;

  int i;
  unsigned char * ptr;


  rawsock = socket(PF_INET,SOCK_RAW,IPPROTO_TCP);

  if (rawsock == -1)
    perror("socket():");

  flags =  MSG_WAITALL;
  memset(&from,0,fromlen);

  bytesread = recvfrom(rawsock,&buf,buflen,flags,
		       (struct sockaddr*)(&from),&fromlen);

  ptr = (unsigned char*)&from;
  for(i=0;i<fromlen;i++) {
      printf("%i  ",*ptr);
      ptr++;
  }
  printf("\n");

  if (bytesread == -1) {
    printf("err # : %i \n",errno);
    perror("recvfrom():");
    return -1;
 }

 
    if (argc ==2) {
      struct hostent *host;

      printf("msg len: %i \n",bytesread);
      printf("frm len: %i \n",fromlen);
      printf("IPv4 : type:%i port:%X addr:%X \n", 
	     from.sin_family,
	     ntohs(from.sin_port),
	     from.sin_addr.s_addr);

      host=gethostbyaddr(&(from.sin_addr.s_addr),
			 fromlen,from.sin_family);

      if (host == NULL ) {
	printf("err # : %i \n",h_errno);
	herror("gethostbyaddr():");
      }

      printf("host: (");

      ptr = (unsigned char*)(&(from.sin_addr.s_addr));
      for(i=0;i<4;i++) {
	printf("%i",*(ptr++));
	if (i<3)
	  printf(".");
      }
      
      if (host == NULL)
	printf(") \n");
      else
	printf(") %s \n",host->h_name);


    }


  return 0;

}