为什么IPAddress.Parse（“ 192.168.001.001”）不起作用，而IPAddress.Parse（“ 192.168.001.001”）却起作用？ [英] Why IPAddress.Parse("192.168.001.001") works while IPAddress.Parse("192.168.001.009") don't?

问题描述

我一直试图从API结果中解析IP地址，在该结果中，IPv4地址的四个Pat均以0（零）为前缀。像这样：

I'm stuck trying to parse IP addresses from a API result where each of the four pats of the IPv4 Address comes prefixed with 0 (zeroes). Something like this:

127.000.000.001而不是127.0.0.1

127.000.000.001 instead of 127.0.0.1

当我尝试解析192.168.001.009对于192.168.001.008，它也会失败，但对于001、007、006、005都有效！!!!

I started getting parse errors when trying to parse 192.168.001.009. It also fails for 192.168.001.008, but works for 007, 006, 005 up to 001!!!

对于192.168.001.018，它也会失败，但是对于.017 ，.016降到010！

It also fails for 192.168.001.018, but works for .017, .016 down to 010!

它适用于192.168.001.8或.8以及192.168.001.18和.19 ...

It works for 192.168.001.8 or .8 and also 192.168.001.18 and .19...

这是CLR中的错误吗？还是我想念一些愚蠢的东西？

Is this a bug in the CLR? Or am I missing something stupid?

只需尝试：

IPAddress.Parse("192.168.001.007"); // works
IPAddress.Parse("192.168.001.87"); // works
IPAddress.Parse("192.168.001.008"); // throws exception
IPAddress.Parse("192.168.001.19"); // works
IPAddress.Parse("192.168.001.019");  // throws exception
// and so on!

推荐答案

数字从0开始，因此被解释为八进制而不是十进制。这些不是C＃文字，因此要由库以一种或另一种方式解释。

The numbers, since they are starting with 0, are being interpreted as octal instead of decimal. These are not C# literals, so it's up to the library to interpret it one way or another.

一种简单的测试方法是构造一个以 .010，解析它，您会看到它被解析为以.8结尾的ip。

A simple way to test it would be to construct an IP ending in ".010", parse it, and you'll see that it was parsed as an ip ending in .8.

一种可能的快速而肮脏的解决方案是搜索正则表达式 /\.0 * / 并替换

A possible quick and dirty solution would be to search for the regex /\.0*/ and replace it with "."

您可以在Wikipedia条目上找到点小数表示法的更多信息：

You can find more information on the wikipedia entry for Dot-decimal-notation:

IP网络的一种流行实现始于4.2BSD，其中包含一个函数inet_aton（），用于将字符串表示形式的IP地址转换为内部二进制存储。除了基本的四进制十进制格式和完整的32位地址外，它还支持octet.24bits（例如10.1234567；对于A类地址）和octet.octet.16bits（例如172.16.12345；对于B类地址）中间语法。 ）。通过分别给数字加上0x和0前缀，它还允许以十六进制和八进制形式写入数字。直到今天，这些功能仍继续受软件支持，即使它们被视为非标准功能也是如此。但这也意味着，用不同的程序可能会以不同的方式来解释用前导零数字写入IP地址组件的地址：有些会忽略前导零，有些则会将数字解释为八进制。

A popular implementation of IP networking, originating in 4.2BSD, contains a function inet_aton() for converting IP addresses in character strings representation to internal binary storage. In addition to the basic four-decimals format and full 32-bit addresses, it also supported intermediate syntaxes of octet.24bits (e.g. 10.1234567; for Class A addresses) and octet.octet.16bits (e.g. 172.16.12345; for Class B addresses). It also allowed the numbers to be written in hexadecimal and octal, by prefixing them with 0x and 0, respectively. These features continue to be supported by software until today, even though they are seen as non-standard. But this also means addresses where an IP address component is written with a leading zero digit may be interpreted differently by different programs: some will ignore the leading zero, some will interpret the number as octal.

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