getaddrinfo iteration example Mac OSX maybe *nix

/*

getaddrinfo example

Authored by:
    bazz

Built for/on OSX, and may be portable to other *nix based systems.
This example demonstrates how to iterate over the linked list
provided by getaddrinfo, to test for successful connection.
Because, without testing, you're never sure that you are passing a
successful ip!!

usage:
 g++ getaddrinfo.cpp -o getaddrinfo
 ./getaddrinfo google.com 80
 ./getaddrinfo google.com http
 same thing

 You will find that most cases succeed on first try.
 Also, it takes awhile for connect to timeout,
 how to adjust this?!

*/



#include <iostream>
#include <sys/types.h>
#include <sys/socket.h>
#include <netdb.h>
#include <err.h>
#include <unistd.h>
#include <arpa/inet.h>

int main(int argc, char **argv)
{
  struct addrinfo hints, *res, *res0;
  int error;
  int s;
  const char *cause = NULL;
  int index=0;
  char ip[100];
  struct sockaddr_in *h;


  memset(&hints, 0, sizeof(hints));
  hints.ai_family = PF_UNSPEC;
  hints.ai_socktype = SOCK_STREAM;
  error = getaddrinfo(argv[1], argv[2], &hints, &res0);
  if (error)
  {
    errx(1, "%s", gai_strerror(error));
    /*NOTREACHED*/
  }
  s = -1;
  for (res = res0; res; res = res->ai_next)
  {
    index++;
    s = socket(res->ai_family, res->ai_socktype,
       res->ai_protocol);
    if (s < 0)
    {
      std::cerr << "socket creation failed" << std::endl;
      cause = "socket";
      continue;
    }

    h = (struct sockaddr_in *) res->ai_addr;
    strcpy(ip , inet_ntoa( h->sin_addr ) );
    std::cerr << "Trying to connect to " << ip << ":" << argv[2] << "; ";

    if (connect(s, res->ai_addr, res->ai_addrlen) < 0) {
           std::cerr << "FAILED" << std::endl;
           cause = "connect";
           close(s);
           s = -1;
           continue;
    }
    std::cerr << "SUCCESS" << std::endl;
    break;  /* okay we got one */
  }
  if (s < 0)
  {
    err(1, "%s", cause);
    /*NOTREACHED*/
  }


  freeaddrinfo(res0);

  std::cout << "Connected to " << argv[1] << " at " << ip << " on try#" << index << std::endl;

  return 0;
}