ho trovato questa funzione,restituisce l' ip,può andare bene?
codice:
int lookup_host (const char *host,char *indip)
{
  struct addrinfo hints, *res;
  int errcode;
  char addrstr[100];
 
  void *ptr;

  memset (&hints, 0, sizeof (hints));
  hints.ai_family = PF_UNSPEC;
  hints.ai_socktype = SOCK_STREAM;
  hints.ai_flags |= AI_CANONNAME;

  errcode = getaddrinfo (host, NULL, &hints, &res);
  if (errcode != 0)
    {
      printf("Host non presente\n");
      return -1;
    }

  //printf ("Host: %s\n", host);
  inet_ntop (res->ai_family, res->ai_addr->sa_data, addrstr, 100);
  int y=0;
  while (res){
      y++;
      inet_ntop (res->ai_family, res->ai_addr->sa_data, addrstr, 100);

      switch (res->ai_family)
        {
        case AF_INET:
          ptr = &((struct sockaddr_in *) res->ai_addr)->sin_addr;
          break;
          
   case AF_INET6:
          ptr = &((struct sockaddr_in6 *) res->ai_addr)->sin6_addr;
          break;
   
        }
   
      inet_ntop (res->ai_family, ptr, addrstr, 100);
      //printf ("IPv%d address: %s (%s)\n", res->ai_family == PF_INET6 ? 6 : 4,
             // addrstr, res->ai_canonname);
      if(y==1) strcpy(indip,      addrstr);
     
      res = res->ai_next;
       
    }
  //printf("---->%s\n",indip);
  return 0;
}