test.c

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


/* man getaddrinfo */

int main()
{
  struct addrinfo *addrinfo = NULL;
  struct addrinfo *rp = NULL;
  struct addrinfo hints;
  struct addrinfo res;
  int err;

  memset((void*)&hints, 0, sizeof(hints));

//  hints.ai_family   = PF_INET4;
//  hints.ai_family   = PF_INET6;
hints.ai_family   = PF_UNSPEC;

  hints.ai_socktype = SOCK_STREAM;
  hints.ai_flags    = AI_PASSIVE;

  err = getaddrinfo("localhost", "18083", &hints, &addrinfo);

  if ( addrinfo )
  {
    for (rp = addrinfo; rp != NULL; rp = rp->ai_next)
    {
      int sa_family = ((struct sockaddr*)rp->ai_addr)->sa_family;

      if ( sa_family == AF_INET6)
      {
        char straddr[INET6_ADDRSTRLEN];
        struct sockaddr_in6* _ai_addr_ptr=(struct sockaddr_in6*)rp->ai_addr;
        struct sockaddr_in6  _ai_addr=*_ai_addr_ptr;

        inet_ntop(AF_INET6, &_ai_addr.sin6_addr, straddr, sizeof(straddr));
        printf("%s\n", straddr);
      }
      else if ( sa_family == AF_INET)
      {
        printf("%s\n", inet_ntoa( ((struct sockaddr_in*)rp->ai_addr)->sin_addr ));
      }
    }

    freeaddrinfo(addrinfo);
    return(0);
  }
  else
  {
    printf("addrinfo->ai_family == 0x%x\n", addrinfo->ai_family);
  }

  if (err || !addrinfo)
  {
    printf("getaddrinfo failed with code %i.\n",err);
    return(1);
  }

  printf("end_main()\n");
  return (0);
}

Test results:

FreeBSD 9.2:

ums4 getaddrinfo/ root~# gcc test.c -o test && ./test
::1
127.0.0.1

Mac OS X 10.7 Lion:

janitors-man-mini getaddrinfo/ id~$ gcc test.c -o test && ./test
127.0.0.1
::1
fe80::1