简单解析DNS

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


int main(int argc, char* argv[])
{
    if (argc <= 1){
        return 0;
    }

    ares_channel channel;
    int status;
    status = ares_library_init(ARES_LIB_INIT_ALL);
    if (status != ARES_SUCCESS){
        puts("Error");
        return 0;
    }
    status = ares_init(&channel);
    if (status != ARES_SUCCESS){
        puts("Error2");
        return 0;
    }

    ares_set_servers_csv(channel, "8.8.8.8");
    ares_gethostbyname(channel, argv[1], AF_INET, [](auto arg, auto status, auto timeouts, auto hosten)->void {
        if (status == ARES_SUCCESS){
            struct in_addr  addr;
            memcpy(&addr, hosten->h_addr_list[0], hosten->h_length);
            printf("IP Address: %s\n", inet_ntoa(addr));
        }
        else{
            printf("DNS resolution failed.\n");
        }
    }, nullptr);

    struct timeval tv;
    tv.tv_sec = 0;
    tv.tv_usec = 0;
    fd_set read_fds, write_fds;
    int nfds = ares_fds(channel, &read_fds, &write_fds);
    while (nfds > 0){
        select(nfds, &read_fds, &write_fds, nullptr, &tv);
        ares_process(channel, &read_fds, &write_fds);
        nfds = ares_fds(channel, &read_fds, &write_fds);
    }
    ares_destroy(channel);
    ares_library_cleanup();
    return 0;
}