Python3--DNS

```python
# -*- coding: utf-8 -*-

# Python

# socket.gethostbyname

import socket

result = socket.gethostbyname("IPv6test.ntes53.netease.com")
print(result)  # # 123.58.166.70
print(type(result))  # # <class 'str'>

# socket.getaddrinfo
# 当不指定 socktype 时，此值默认为 socket.AF_UNSPEC。
result1 = socket.getaddrinfo("IPv6test.ntes53.netease.com", 0, socket.AF_INET6)
print(result1)  #socket.gaierror: [Errno 11004] getaddrinfo failed ## getaddrinfo失败
result2 = socket.getaddrinfo("IPv6test.ntes53.netease.com", 0, socket.AF_INET)
print(result2)  # # [(<AddressFamily.AF_INET: 2>, 0, 0, '', ('123.58.166.70', 0))]
result3 = socket.getaddrinfo("IPv6test.ntes53.netease.com", 0, socket.AF_UNSPEC)
print(result3)  # # [(<AddressFamily.AF_INET: 2>, 0, 0, '', ('123.58.166.70', 0))]
'''
ipv4环境下使用 socket.getaddrinfo("IPv6test.ntes53.netease.com", 0, socket.AF_INET6) 解析ipv6地址，程序会报错，
ipv6环境下解析结果如下：
123.58.166.70
<class 'str'>
[(<AddressFamily.AF_INET6: 23>, 0, 0, '', ('2403:c80:100:3000::7b3a:a646', 0, 0, 0))]
[(<AddressFamily.AF_INET: 2>, 0, 0, '', ('123.58.166.70', 0))]
[(<AddressFamily.AF_INET6: 23>, 0, 0, '', ('2403:c80:100:3000::7b3a:a646', 0, 0, 0)), (<AddressFamily.AF_INET: 2>, 0, 0, '', ('123.58.166.70', 0))]
'''
```

如果指定AF_INET，那么函数就不能返回任何IPV6相关的地址信息；
如果仅指定了AF_INET6，则就不能返回任何IPV4地址信息。
AF_UNSPEC则意味着函数返回的是适用于指定主机名和服务名且适合任何协议族的地址。

如果某个主机既有AAAA记录(IPV6)地址，同时又有A记录(IPV4)地址，那么AAAA记录将作为sockaddr_in6结构返回，而A记录则作为sockaddr_in结构返回;

链接：https://www.jianshu.com/p/1efcc2a6aaf0