c-ares

c

#include <stdio.h>
#include <ares.h>
#include <arpa/inet.h>
#include <netdb.h>

void callback(void *arg, int status, int timeouts, struct hostent *host) {
    if (status == ARES_SUCCESS) {
        char ip[INET6_ADDRSTRLEN];
        int idx;

        for (idx = 0; host->h_addr_list[idx]; ++idx) {
            inet_ntop(host->h_addrtype, host->h_addr_list[idx], ip, sizeof(ip));
            printf("%s\n", ip);
        }
    } else {
        printf("Failed to lookup: %s\n", ares_strerror(status));
    }
}

int main(int argc, char **argv) {
    ares_channel channel;
    int nfds, rv;
    fd_set read_fds, write_fds;
    struct timeval *tvp, tv;
    
    if (ares_library_init(ARES_LIB_INIT_ALL)) {
        return 1; // Initialization failure
    }

    if (ares_init(&channel) != ARES_SUCCESS) {
        ares_library_cleanup();
        return 1; // Initialization failure
    }

    ares_gethostbyname(channel, "www.google.com", AF_INET, callback, NULL);

    while (1) {
        FD_ZERO(&read_fds);
        FD_ZERO(&write_fds);
        nfds = ares_fds(channel, &read_fds, &write_fds);
        if (nfds == 0) {
            break; // All queries completed
        }

        tvp = ares_timeout(channel, NULL, &tv);
        rv = select(nfds, &read_fds, &write_fds, NULL, tvp);

        if (rv < 0) {
            printf("Error in select()\n");
            ares_cancel(channel);
        } else if (rv == 0) {
            ares_process(channel, NULL, NULL); // Timeout
        } else {
            ares_process(channel, &read_fds, &write_fds); // Process results
        }
    }

    ares_destroy(channel);
    ares_library_cleanup();
    return 0;
}