c# - IPAddress.TryParse 返回不需要的结果

Question

我有一个函数，它使用 IPAddress 类返回给定 IP 地址是否有效。我正在测试它，即使我在没有点作为参数的情况下传递“0123456”或“11111”或“99999”，它也会返回有效(真)。我用 VB.net 和 C# 编写了它，结果相同。

// C#
public bool CheckIpAddress(string ipAddr)
{
    IPAddress ip = null;
    return IPAddress.TryParse(ipAddr,out ip);
}

  // VB.net
  Public Function CheckIpAddress(ipAddr As String) As Boolean
        Dim ip As IPAddress = Nothing

        Return Net.IPAddress.TryParse(ipAddr, ip)
    End Function

有人能解释一下为什么会这样吗？我已经通过互联网将我的代码与一些资源进行了匹配，没有问题。

Answer 1

IP 地址只是 32 位数字，所以 11111 绝对是一个正确的 IP 地址。 IP 地址中的点只是为了让人们更容易阅读它们。它们不是必需的。

IP addresses are binary numbers, but they are usually stored in text files and displayed in human-readable notations, such as 172.16.254.1 (for IPv4), and 2001:db8:0:1234:0:567:8:1 (for IPv6).

from IP address - Wikipedia

这就是 IPAddress.TryParse 返回 true 的原因。

它甚至在 MSDN 上有描述:IPAddress.Parse Method

The number of parts (each part is separated by a period) in ipString determines how the IP address is constructed. A one part address is stored directly in the network address. A two part address, convenient for specifying a class A address, puts the leading part in the first byte and the trailing part in the right-most three bytes of the network address. A three part address, convenient for specifying a class B address, puts the first part in the first byte, the second part in the second byte, and the final part in the right-most two bytes of the network address.

还有一个例子(见第一个):

1 -- "65536"       0.0.255.255
2 -- "20.2"        20.0.0.2
2 -- "20.65535"    20.0.255.255
3 -- "128.1.2"     128.1.0.2