刚刚测试程序，一个功能要求获取客户端IP，然而在本机测试过程中发现，客户端(本机)IP始终返回::1，获取 IP 部份的代码如下：
{
string result = String.Empty;
result = HttpContext.Current.Request.ServerVariables["HTTP_X_FORWARDED_FOR"];
if (null == result || result == String.Empty)
{
result = HttpContext.Current.Request.ServerVariables["REMOTE_ADDR"];
}
if (null == result || result == String.Empty)
{
result = HttpContext.Current.Request.UserHostAddress;
}
if (null == result || result == String.Empty || !IsIP(result))
{
result = "0.0.0.0";
}
return result;
}
public static bool IsIP(string ip)
{
return Regex.IsMatch(ip, @"^((2[0-4]\d|25[0-5]|[01]?\d\d?)\.){3}(2[0-4]\d|25[0-5]|[01]?\d\d?)$");
}
于是最终获取倒的是因无法匹配而返回的默认IP 0.0.0.0
google了一下，没有结果。
继续想办法。发现不影响获取其它客户端（非本机）IP。根据此现象，我想应该是localhost引起的，于是查看host映射，果然发现::1
(Host映射查看方法 C:\Windows\System32\drivers\etc 文件hosts)
# Copyright (c) 1993-2006 Microsoft Corp.
#
# This is a sample HOSTS file used by Microsoft TCP/IP for Windows.
#
# This file contains the mappings of IP addresses to host names. Each
# entry should be kept on an individual line. The IP address should
# be placed in the first column followed by the corresponding host name.
# The IP address and the host name should be separated by at least one
# space.
#
# Additionally, comments (such as these) may be inserted on individual
# lines or following the machine name denoted by a '#' symbol.
#
# For example:
#
# 102.54.94.97 rhino.acme.com # source server
# 38.25.63.10 x.acme.com # x client host
127.0.0.1 localhost
::1 localhost
原来是因为操作系统开启了IPV6，它对localhost进行了映射的原因。如果我们需要获取的IP是IPV4的，那么可以删掉::1映射。
如果将来我们需要获取的是IPV6的IP，那么就需要这样的映射。然后程序里统一实现获取IPv6的代码。