描述：
​		服务端在接收客户端请求的时候，为了保证系统的安全性，一般在服务端需要进行签名认证或者是对客户端ip进行访问控制，那么进行 ip 控制时，我们首先需要获取客户端请求的真实 ip 地址；
情况1：客户端未经过任何代理，直接访问服务器
String ip = request.getRemoteAddr() // 直接获取客户端 ip

情况2：客户端经过多级代理，最终访问服务器
/** 
* 获取当前网络ip 
* @param request 请求
* @return 
*/  
public String getIpAddr(HttpServletRequest request){  
    String ipAddress = request.getHeader("x-forwarded-for");  
    if(ipAddress == null || ipAddress.length() == 0 || "unknown".equalsIgnoreCase(ipAddress)) {  
        ipAddress = request.getHeader("Proxy-Client-IP");  
    }  
    if(ipAddress == null || ipAddress.length() == 0 || "unknown".equalsIgnoreCase(ipAddress)) {  
        ipAddress = request.getHeader("WL-Proxy-Client-IP");  
    }  
    if(ipAddress == null || ipAddress.length() == 0 || "unknown".equalsIgnoreCase(ipAddress)) {  
        ipAddress = request.getRemoteAddr();  
        if(ipAddress.equals("127.0.0.1") || ipAddress.equals("0:0:0:0:0:0:0:1")){  
            // 根据网卡取本机配置的IP  
            InetAddress inet=null;  
            try {  
                inet = InetAddress.getLocalHost();  
            } catch (UnknownHostException e) {  
                e.printStackTrace();  
            }  
            ipAddress= inet.getHostAddress();  
        }  
    }  
    // 对于经过多个代理的情况 第一个IP为客户端真实IP 多个IP按照','分割  
    if(ipAddress!=null && ipAddress.length()>15){ //"***.***.***.***".length() = 15  
        if(ipAddress.indexOf(",")>0){  
            ipAddress = ipAddress.substring(0,ipAddress.indexOf(","));  
        }  
    }  
    return ipAddress;   
}

package com.tao.Util;
 
import javax.servlet.http.HttpServletRequest;
import java.net.Inet4Address;
import java.net.InetAddress;
import java.net.NetworkInterface;
import java.net.SocketException;
import java.util.Enumeration;
import java.util.HashMap;
import java.util.Map;
 
 
public class HostUtil {
    private static String ipstr = "127.0.0.1";
    private static Map<String, String> map = new HashMap();
 
    static {
        map.put("ip", getLinuxLocalIp());
    }
 
    public static String getHostIp() {
        String ip = map.get("ip");
        if (ip == null) {
            String ip1 = getLinuxLocalIp();
            map.put("ip", ip1);
            return ip1;
        }
        return ip;
    }
    
 
    /**
     * 获取Linux下的IP地址
     *
     * @return IP地址
     * @throws SocketException
     */
    private static String getLinuxLocalIp() {
        String ip = "";
        try {
            for (Enumeration<NetworkInterface> en = NetworkInterface.getNetworkInterfaces(); en.hasMoreElements(); ) {
                NetworkInterface intf = en.nextElement();
                String name = intf.getName();
                if (!name.contains("docker") && !name.contains("lo")) {
                    for (Enumeration<InetAddress> enumIpAddr = intf.getInetAddresses(); enumIpAddr.hasMoreElements(); ) {
                        InetAddress inetAddress = enumIpAddr.nextElement();
                        if (!inetAddress.isLoopbackAddress()) {
                            String ipaddress = inetAddress.getHostAddress().toString();
                            if (!ipaddress.contains("::") && !ipaddress.contains("0:0:") && !ipaddress.contains("fe80")) {
                                ip = ipaddress;
                            }
                        }
                    }
                }
            }
        } catch (SocketException ex) {
            ip = "127.0.0.1";
            ex.printStackTrace();
        }
        return ip;
    }
 
    /**
     * 获取请求者的ip地址
     *
     * @param request
     * @return
     */
    public static String getIpAdrress(HttpServletRequest request) {
        String ip = null;
 
        //X-Forwarded-For：Squid 服务代理
        String ipAddresses = request.getHeader("X-Forwarded-For");
        String unknown = "unknown";
        if (ipAddresses == null || ipAddresses.length() == 0 || unknown.equalsIgnoreCase(ipAddresses)) {
            //Proxy-Client-IP：apache 服务代理
            ipAddresses = request.getHeader("Proxy-Client-IP");
        }
 
        if (ipAddresses == null || ipAddresses.length() == 0 || unknown.equalsIgnoreCase(ipAddresses)) {
            //WL-Proxy-Client-IP：weblogic 服务代理
            ipAddresses = request.getHeader("WL-Proxy-Client-IP");
        }
 
        if (ipAddresses == null || ipAddresses.length() == 0 || unknown.equalsIgnoreCase(ipAddresses)) {
            //HTTP_CLIENT_IP：有些代理服务器
            ipAddresses = request.getHeader("HTTP_CLIENT_IP");
        }
 
        if (ipAddresses == null || ipAddresses.length() == 0 || unknown.equalsIgnoreCase(ipAddresses)) {
            //X-Real-IP：nginx服务代理
            ipAddresses = request.getHeader("X-Real-IP");
        }
 
        //有些网络通过多层代理，那么获取到的ip就会有多个，一般都是通过逗号（,）分割开来，并且第一个ip为客户端的真实IP
        if (ipAddresses != null && ipAddresses.length() != 0) {
            ip = ipAddresses.split(",")[0];
        }
 
        //还是不能获取到，最后再通过request.getRemoteAddr();获取
        if (ip == null || ip.length() == 0 || unknown.equalsIgnoreCase(ipAddresses)) {
            ip = request.getRemoteAddr();
        }
        return ip;
    }
 
 
}

 

package com.tao.Util;

import javax.servlet.http.HttpServletRequest;
import java.net.Inet4Address;
import java.net.InetAddress;
import java.net.NetworkInterface;
import java.net.SocketException;
import java.util.Enumeration;
import java.util.HashMap;
import java.util.Map;


public class HostUtil {
    private static String ipstr = "127.0.0.1";
    private static Map<String, String> map = new HashMap();

    static {
        map.put("ip", getLinuxLocalIp());
    }

    public static String getHostIp() {
        String ip = map.get("ip");
        if (ip == null) {
            String ip1 = getLinuxLocalIp();
            map.put("ip", ip1);
            return ip1;
        }
        return ip;
    }
    

    /**
     * 获取Linux下的IP地址
     *
     * @return IP地址
     * @throws SocketException
     */
    private static String getLinuxLocalIp() {
        String ip = "";
        try {
            for (Enumeration<NetworkInterface> en = NetworkInterface.getNetworkInterfaces(); en.hasMoreElements(); ) {
                NetworkInterface intf = en.nextElement();
                String name = intf.getName();
                if (!name.contains("docker") && !name.contains("lo")) {
                    for (Enumeration<InetAddress> enumIpAddr = intf.getInetAddresses(); enumIpAddr.hasMoreElements(); ) {
                        InetAddress inetAddress = enumIpAddr.nextElement();
                        if (!inetAddress.isLoopbackAddress()) {
                            String ipaddress = inetAddress.getHostAddress().toString();
                            if (!ipaddress.contains("::") && !ipaddress.contains("0:0:") && !ipaddress.contains("fe80")) {
                                ip = ipaddress;
                            }
                        }
                    }
                }
            }
        } catch (SocketException ex) {
            ip = "127.0.0.1";
            ex.printStackTrace();
        }
        return ip;
    }

    /**
     * 获取请求者的ip地址
     *
     * @param request
     * @return
     */
    public static String getIpAdrress(HttpServletRequest request) {
        String ip = null;

        //X-Forwarded-For：Squid 服务代理
        String ipAddresses = request.getHeader("X-Forwarded-For");
        String unknown = "unknown";
        if (ipAddresses == null || ipAddresses.length() == 0 || unknown.equalsIgnoreCase(ipAddresses)) {
            //Proxy-Client-IP：apache 服务代理
            ipAddresses = request.getHeader("Proxy-Client-IP");
        }

        if (ipAddresses == null || ipAddresses.length() == 0 || unknown.equalsIgnoreCase(ipAddresses)) {
            //WL-Proxy-Client-IP：weblogic 服务代理
            ipAddresses = request.getHeader("WL-Proxy-Client-IP");
        }

        if (ipAddresses == null || ipAddresses.length() == 0 || unknown.equalsIgnoreCase(ipAddresses)) {
            //HTTP_CLIENT_IP：有些代理服务器
            ipAddresses = request.getHeader("HTTP_CLIENT_IP");
        }

        if (ipAddresses == null || ipAddresses.length() == 0 || unknown.equalsIgnoreCase(ipAddresses)) {
            //X-Real-IP：nginx服务代理
            ipAddresses = request.getHeader("X-Real-IP");
        }

        //有些网络通过多层代理，那么获取到的ip就会有多个，一般都是通过逗号（,）分割开来，并且第一个ip为客户端的真实IP
        if (ipAddresses != null && ipAddresses.length() != 0) {
            ip = ipAddresses.split(",")[0];
        }

        //还是不能获取到，最后再通过request.getRemoteAddr();获取
        if (ip == null || ip.length() == 0 || unknown.equalsIgnoreCase(ipAddresses)) {
            ip = request.getRemoteAddr();
        }
        return ip;
    }


}

 

随着ASP.NET的发展，有不同的方式从请求中访问客户端IP地址。WebForms和MVC Web应用程序只是访问当前HTTP上下文的请求。
var ip = HttpContext.Current.Request.UserHostAddress;
或者只是直接引用当前的Request
var ip = Request.UserHostAddress;
但是，这在ASP.NET Core 2.0及更高版本中不起作用。您必须从ConfigureServices方法中的Startup.cs类中注入HttpContextAccessor实例。
public void ConfigureServices(IServiceCollection services)
{
services.AddSingleton();
services.AddMvc();
}
现在我们需要在我们的控制器构造函数中使用它并将其分配给控制器级别声明的变量，这样，它可以从控制器中的所有Actions访问，注意我们这里还使用了NetworkInterface.GetAllNetworkInterfaces()方法来获取服务器上所有网卡的IP地址：
using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.Http;
using System.Net;
using System.Net.NetworkInformation;
using System.Linq;
using System.Net.Sockets;
namespace AspNetCoreIP.Controllers
{
public class HomeController : Controller
{
protected readonly IHttpContextAccessor httpContextAccessor;
public HomeController(IHttpContextAccessor httpContextAccessor)
{
this.httpContextAccessor = httpContextAccessor;
}
public IActionResult Index()
{
//获取客户端的IP地址
string clientIpAddress = httpContextAccessor.HttpContext.Connection.RemoteIpAddress.MapToIPv4().ToString();
this.ViewData["ClientIpAddress"] = clientIpAddress;
//获取服务器上所有网卡的IP地址
NetworkInterface[] networks = NetworkInterface.GetAllNetworkInterfaces();
string serverIpAddresses = string.Empty;
foreach (var network in networks)
{
var ipAddress = network.GetIPProperties().UnicastAddresses.Where(p => p.Address.AddressFamily == AddressFamily.InterNetwork && !IPAddress.IsLoopback(p.Address)).FirstOrDefault()?.Address.ToString();
serverIpAddresses += network.Name + ":" + ipAddress + "|";
}
this.ViewData["ServerIpAddresses"] = serverIpAddresses;
return View();
}
}
}
建立MVC视图Index.cshtml，来显示客户端和服务器端的IP地址：
@{
Layout = null;
}
Index
客户端IP地址:@this.ViewData["ClientIpAddress"].ToString()
服务器所有网卡的IP地址:@this.ViewData["ServerIpAddresses"].ToString()
为什么有时候httpContextAccessor.HttpContext.Connection.RemoteIpAddress获取到的客户端IP地址为空，请参见下文链接：
https://www.cnblogs.com/OpenCoder/category/1132736.html