#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h>
#include <arpa/inet.h>
#include <string.h>
#include <stdio.h>

int MakeSocketAddr(
    struct sockaddr *sockaddrPtr,  /* socket address */
    char *hostname,       /* name or ip of host. NULL implies INADDR_ANY */
    int port,             /* port number */
    char dotted_ip[16]) { /* resolved ip addr */
  /*
    Workaround for cases, where the local cache is not updated (yet)
    often, gethostbyname gets a cached value, but dig will get a fresh one
    note after an internet research: dig is recommended over nslookup
  */

  struct hostent *hostent;      /* Host database entry */
  struct sockaddr_in *sadr = (struct sockaddr_in *)sockaddrPtr;
  FILE *fil;
  char line[256];
  int l;

  (void) memset(sadr, 0, sizeof(*sadr));
  if (dotted_ip) { /* default value: failure */
    dotted_ip[0] = 0;
  }
  sadr->sin_family = AF_INET;
  sadr->sin_port = htons((unsigned short)port);
  if (hostname == NULL) {
    /* do not need to copy, as INADDR_ANY is all zero bytes */
    return 1;
  }
  if (inet_pton(AF_INET, hostname, &sadr->sin_addr) == 1) {
    /* resolved as dotted numbers notation */
    return 1;
  }
  hostent = gethostbyname(hostname);
  if (hostent == 0) {
    /* we assume that when gethostname gets no entry, dig will also fail.
    That way, dig will not be called repeatedly for no reason */
    return 0;
  }
  /* copy the address: in case dig fails, we use the cached value */
  memcpy(&sadr->sin_addr, hostent->h_addr_list[0], 4);
  /* we use hostent->h_name instead of hostname here, as this has already
     the proper domain added */
  snprintf(line, sizeof line, "timeout 1 dig +short %s", hostent->h_name);
  fil = popen(line, "r");
  if (fil != NULL) {
    if (fgets(line, sizeof(line), fil) != NULL) {
      l = strlen(line);
      if (line[l-1] <= ' ') line[l-1] = 0; /* strip off newline */
      /* silently ignore return value, if it fails, we take the cached value */
      inet_pton(AF_INET, line, &sadr->sin_addr);
    }
    fclose(fil);
  }
  if (dotted_ip) {
    inet_ntop(AF_INET, &sadr->sin_addr, dotted_ip, 16);
  }
  return 1;
}

int CreateSocketAdress(struct sockaddr_in *sockaddrPtr,  /* Socket address */
                       char *host,       /* Host.  NULL implies INADDR_ANY */
                       int port)
{
   return MakeSocketAddr((struct sockaddr *)sockaddrPtr, host, port, NULL);
}