C++ 实现域名与 IP 地址相互解析示例

Windows 平台

#include <iostream>
#include <winsock2.h>
#include <ws2tcpip.h>
#pragma comment(lib, "ws2_32.lib")

int main() {
    WSADATA wsaData;
    if (WSAStartup(MAKEWORD(2, 2), &wsaData) != 0)
        std::cout << "WSAStartup() error" << std::endl;

    auto host = gethostbyname("www.bdjw.work");
    if (host) {
        //主域名
        std::cout << host->h_name << std::endl;
        //ip 地址长度，ipv4 是 4 字节
        std::cout << host->h_length << std::endl;
        //IP 地址族信息
        if (AF_INET == host->h_addrtype)
            std::cout << "AF_INET" << std::endl;
        else
            std::cout << host->h_addrtype << std::endl;
        //如果有其它域名，是由 h_aliases 保存
        for (size_t i = 0; host->h_aliases[i]; i++)
            std::cout << host->h_aliases[i] << std::endl;
        //IP 地址列表
        for (size_t i = 0; host->h_addr_list[i]; i++)
            std::cout << inet_ntoa(*(in_addr*)host->h_addr_list[i]) << std::endl;
    }

    SOCKADDR_IN addr;
    memset(&addr, 0, sizeof(addr));
    addr.sin_addr.s_addr = inet_addr("101.43.87.248");
    host = gethostbyaddr((char*)&addr.sin_addr, 4, AF_INET);
    if (host) {
        //主域名
        std::cout << host->h_name << std::endl;
        //ip 地址长度，ipv4 是 4 字节
        std::cout << host->h_length << std::endl;
        //IP 地址族信息
        if (AF_INET == host->h_addrtype)
            std::cout << "AF_INET" << std::endl;
        else
            std::cout << host->h_addrtype << std::endl;
        //如果有其它域名，是由 h_aliases 保存
        for (size_t i = 0; host->h_aliases[i]; i++)
            std::cout << host->h_aliases[i] << std::endl;
        //IP 地址列表
        for (size_t i = 0; host->h_addr_list[i]; i++)
            std::cout << inet_ntoa(*(in_addr*)host->h_addr_list[i]) << std::endl;
    }
    WSACleanup();
    return 0;
}

注意：gethostbyname 和 gethostbyaddr 为 POSIX 标准函数，在较新系统中建议使用 getaddrinfo 替代。