将ip解析为hostname

Question

我正在尝试从IP地址解析主机名.我尝试过使用gethostbyaddr(),getnameinfo()但在很多情况下,主机名根本没有解决.有没有更好的方法将IP地址转换为有效的主机名？

char* ip = argv[1];
// using gethostbyaddr()
hostent * phe = gethostbyaddr(ip, strlen(ip), AF_INET);
if(phe) {
  cout << phe->h_name << "\n";
}

// using getnameinfo()
char hostname[260];
char service[260];
sockaddr_in address;
memset(&address, 0, sizeof(address));
address.sin_family = AF_INET;
address.sin_addr.s_addr = inet_addr(ip);
int response = getnameinfo((sockaddr*)&address, 
                            sizeof(address), 
                            hostname, 
                            260, 
                            service, 
                            260, 
                            0);
if(response == 0) {
  cout << hostname << "\n";
}

Answer 1

我尝试过使用gethostbyaddr()和getnameinfo()[...].有没有更好的方法将IP地址转换为有效的主机名？

不,getnameinfo()是选择的方法.

您可以检查getnameinfo()反对的结果EAI_AGAIN,如果相等则重试请求.

收到EAI_OVERFLOW并不意味着你没有回应.无论如何,当你提供259个字符来把结果放在你身上时,很可能不会得到EAI_OVERFLOW...... ;-)

顺便说一句:兴奋剂是正确的,因为他坚持getaddrinfo()和getnameinfo()......的评论 - gethostbyaddr()并且gethostbyname()在某种程度上被弃用了.处理它们的结果也很复杂,并且往往会引起编程错误.

Answer 2

我正在使用Windows这么抱歉(你可以跳过WSADATA部分,如果你正在使用*nix)关于这个版本:)

  #include <stdio.h>
  #include <stdlib.h>
  #include <stdint.h>

  #include <winsock2.h>

  int main(){
    struct addrinfo    hints;
    struct addrinfo   *res=0;
    int       status;

    WSADATA   wsadata;
    int statuswsadata;
    if((statuswsadata=WSAStartup(MAKEWORD(2,2),&wsadata))!=0){
      printf("WSAStartup failed: %d\n",statuswsadata);
    }

    hints.ai_family   =AF_INET;

    status=getaddrinfo("87.250.251.11",0,0,&res);

    {
      char host[512],port[128];

      status=getnameinfo(res->ai_addr,res->ai_addrlen,host,512,0,0,0);

      printf("Host: %s",host);

      freeaddrinfo(res);
    }
  }

我明白了:

d:\temp\stack>ip
Host: yandex.ru

87.250.251.11这是主机yandex.ru的网络地址:

C:\Users\user>ping yandex.ru

Pinging yandex.ru [87.250.251.11] with 32 bytes of data:
Reply from 87.250.251.11: bytes=32 time=21ms TTL=56
Reply from 87.250.251.11: bytes=32 time=21ms TTL=56
Reply from 87.250.251.11: bytes=32 time=21ms TTL=56

Ping statistics for 87.250.251.11:
    Packets: Sent = 3, Received = 3, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
    Minimum = 21ms, Maximum = 21ms, Average = 21ms

希望这可以帮助.