How to test if hostname refers to local machine

Question

Can anyone think of an easy way to tell in win32 or .NET if hostname (string) resolves to a local computer? Such as:

"myhostname"
"myhostname.mydomain.local"
"192.168.1.1"
"localhost"

The goal of this exercise is to produce a test which will tell if Windows security layer will treat access to machine as local or network

Answer 1

In .NET you can:

IPHostEntry iphostentry = Dns.GetHostEntry (Dns.GetHostName ());

Then for any host name, check if it resolves to one of the IPs in iphostEntry.AddressList (this is an IPAddress[]).

Here is a full program that will check the host names/IP addresses passed in the command line:

using System;
using System.Net;

class Test {
    static void Main (string [] args)
    {
     IPHostEntry iphostentry = Dns.GetHostEntry (Dns.GetHostName ());
     foreach (string str in args) {
      IPHostEntry other = null;
      try {
       other = Dns.GetHostEntry (str);
      } catch {
       Console.WriteLine ("Unknown host: {0}", str);
       continue;
      }
      foreach (IPAddress addr in other.AddressList) {
       if (IPAddress.IsLoopback (addr) || Array.IndexOf (iphostentry.AddressList, addr) != -1) {
        Console.WriteLine ("{0} IsLocal", str);
        break;
       } 
      }
     }
    }
}

Answer 2

You can get the IP address that the hostname resolves to by writing Dns.Resolve(hostName).AddressList[0].ToString().

You can then compare that to 127.0.0.1 or to the computer's local IP address.

You can get the computer's local IP addresses by looping through System.Net.Dns.GetHostByName(System.Net.Dns.GetHostName()).AddressList.

Answer 3

In .net you should be able to use Request.ServerVariables(“REMOTE_ADDR”); to get the host ip address and then compare it with the resolved ip address of the hostname. Isn't that what you wanted?