DNS resolve using c-ares

c-ares-test.c

#include <ares.h>
#include <stdio.h>
#include <netdb.h>
#include <assert.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/select.h>

#define HOST_TO_RESOLVE "yandex.ru"

#define GOOGLE_DNS_SERVER 0x08080808
#define DNS_WATCH_SERVER  0x54C84550

static void ares_lookup_completed(void * arg, int status, int timeouts, struct hostent * hostent)
{
    if (status != ARES_SUCCESS)
    {
        printf("Unable to resolve host %s\n", HOST_TO_RESOLVE);
        goto done;
    }

    printf("Resolved host: %u.%u.%u.%u for %s\n", (unsigned char)hostent->h_addr[0],
                                                  (unsigned char)hostent->h_addr[1],
                                                  (unsigned char)hostent->h_addr[2],
                                                  (unsigned char)hostent->h_addr[3],
                                                  hostent->h_name);
done:
    return;
}

int main()
{
    ares_channel channel;

    int nfds, count;
    fd_set readers, writers;
    struct timeval tv, *tvp;

    struct in_addr dns_servers[] = {
        { .s_addr = GOOGLE_DNS_SERVER },
        { .s_addr = DNS_WATCH_SERVER  },
    };

    struct ares_options options = {
        .servers  = dns_servers,
        .nservers = 2
    };

    printf("Initializing c-ares...");
    assert(ARES_SUCCESS == ares_init_options(&channel, &options, ARES_OPT_SERVERS));
    printf("\tOK\n");

    printf("Trying to resolve host %s...\n", HOST_TO_RESOLVE);
    ares_gethostbyname(channel, HOST_TO_RESOLVE, AF_INET, ares_lookup_completed, NULL);

    while (1)
    {
        FD_ZERO(&readers);
        FD_ZERO(&writers);
        nfds = ares_fds(channel, &readers, &writers);
        if (nfds == 0)
        {
            break;
        }

        tvp = ares_timeout(channel, NULL, &tv);
        count = select(nfds, &readers, &writers, NULL, tvp);
        ares_process(channel, &readers, &writers);

        sleep(1);
    }


    printf("Destroying c-ares...");
    ares_destroy(channel);
    printf("\tOK\n");

    return EXIT_SUCCESS;
}