服务端：

//方法一

HttpContext.Current.Request.UserHostAddress;

//方法二

HttpContext.Current.Request.ServerVariables["REMOTE_ADDR"];

//方法三

string strHostName = System.Net.Dns.GetHostName();

string clientIPAddress = System.Net.Dns.GetHostAddresses(strHostName).GetValue(0).ToString();

//方法四（无视代理）

HttpContext.Current.Request.ServerVariables["HTTP_X_FORWARDED_FOR"];

客户端：

//方法五

var ip = '<!--#echo var="REMOTE_ADDR"-->';

alert("Your IP address is "+ip);

//方法六（无视代理）

function GetLocalIPAddress()

{

var obj = null;

var rslt = "";

try

{

obj = new ActiveXObject("rcbdyctl.Setting");

rslt = obj.GetIPAddress;

obj = null;

}

catch(e)

{

//

}

return rslt;

}

来自印度的MCT Maulik Patel提供了一种服务端的解决方案，很好：

if(Context.Request.ServerVariables["HTTP_VIA"]!=null) // using proxy

{

ip=Context.Request.ServerVariables["HTTP_X_FORWARDED_FOR"].ToString(); // Return real client IP.

}

else// not using proxy or can't get the Client IP

{

ip=Context.Request.ServerVariables["REMOTE_ADDR"].ToString(); //While it can't get the Client IP, it will return proxy IP.

}

外加一种 最实用的：

 这个要using System.Net;

        /// <summary>
        /// 获取ip地址
        /// </summary>
        /// <returns></returns>
        private string GetIpAddress()
        {
            string ipAddress = "127.0.0.1";
            IPAddress[] ips = Dns.GetHostAddresses(Dns.GetHostName());
            foreach (IPAddress ip in ips)
            {
                if (ip.AddressFamily.ToString().ToLower().Equals("internetwork"))
                {
                    ipAddress = ip.ToString();
                    return ipAddress;
                }
            }

            return ipAddress;
        }