How does ASP. NET obtain the client's Internet IP address?

Use request. servervariables ("remote_addr") to obtain the IP address of the client, but if the client is accessed by the proxy server, the obtained IP address is the IP address of the proxy server, not the real IP address of the client.

To obtain the real IP address of the client through the proxy server, use request. servervariables ("http_x_forwarded_for") to read.

However, not every proxy server can use request. servervariables ("http_x_forwarded_for") to read the real IP address of the client, some of which are still the IP address of the proxy server.

Note that if the client is not accessed through the proxy server, the value obtained using request. servervariables ("http_x_forwarded_for") will be null. Therefore, if you want to use this method in the program, you can do this:
......
Userip = request. servervariables ("http_x_forwarded_for ")
If userip = "" Then userip = request. servervariables ("remote_addr ")
......

// Method 1
Httpcontext. Current. Request. userhostaddress;

// Method 2
Httpcontext. Current. Request. servervariables ["remote_addr"];

// Method 3
String strhostname = system. net. DNS. gethostname ();
String clientipaddress = system. net. DNS. gethostaddresses (strhostname). getvalue (0). tostring ();

// Method 4 (ignore proxy)
Httpcontext. Current. Request. servervariables ["http_x_forwarded_for"];

Client:

// Method 5
VaR IP = '<! -- # Echo Var = "remote_addr" --> ';
Alert ("your IP address is" + IP );

// Method 6 (ignore proxy)
Function getlocalipaddress ()
{
VaR OBJ = NULL;
VaR rslt = "";
Try
{
OBJ = new activexobject ("rcbdyctl. Setting ");
Rslt = obj. getipaddress;
OBJ = NULL;
}
Catch (E)
{
//
}

Return rslt;
}

MCT Maulik Patel from India provides a server-side solution, which is good:

If (context. Request. servervariables ["http_via"]! = NULL) // server, using proxy
{
Obtain the real client address
IP = context. Request. servervariables ["http_x_forwarded_for"]. tostring (); // return real client IP.
}
Else // if no proxy server is used or the client's IP address is not using proxy or can't get the client IP Address
{

Get the server address
IP = context. Request. servervariables ["remote_addr"]. tostring (); // while it can't get the client IP, it will return proxy IP.
}
Some clients will not send us IP addresses because of the "header_access deny" security settings.

from:http://hi.baidu.com/snake1964/blog/item/055b78cb7bb0f513bf09e6f0.html

Personal applications:

  string GetIp()  
  {
      //string userIP = Request.ServerVariables["HTTP_X_FORWARDED_FOR"];  
      //if (userIP == null || userIP == "")  
      //{  
      //userIP = Request.ServerVariables["REMOTE_ADDR"];  

      //}  
      //  return userIP;        
      string result = String.Empty;

      result = HttpContext.Current.Request.ServerVariables["HTTP_X_FORWARDED_FOR"];
      if (string.IsNullOrEmpty(result))
      {
          result = HttpContext.Current.Request.ServerVariables["REMOTE_ADDR"];
      }

      if (string.IsNullOrEmpty(result))
      {
          result = HttpContext.Current.Request.UserHostAddress;
      }

      if (string.IsNullOrEmpty(result) || !IsIP(result))
      {
          return "127.0.0.1";
      }

      return result;

    }