How To Get IP Address Of A Machine

Introduction

This article is not a technical overview or large discussion. It is like a collection of tips on how you can get the IP address or host name of a machine. In the Win32 API this could be accomplished using the NetWork API. And this is still true in the .NET framework. The only difference is finding and understanding what namespace and class to use to accomplish this task. In the .NET framework the NetWork API is available in the System.Net namespace. The DNS class in the System.Net namespace can be used to get the hostname of a machine or get the IP address if the hostname is already known. The DNS class provides a simple domain name resolution functionality. The DNS class is a static class that provides access to information from the Internet Domain Name System (DNS). The information returned includes multiple IP addresses and aliases if the host specified has more than one entry in the DNS database. The list is returned as a collection or an array of IPAddress objects. The following section is the code that shows how to obtain the IP address for a given host name.

DNSUtility Code

namespace NKUtilities 
{
    using System;
    using System.Net;
    
    public class DNSUtility
    {
        public static int Main (string [] args)
        {
        
          String strHostName = new String ("");
          if (args.Length == 0)
          {
              // Getting Ip address of local machine...
              // First get the host name of local machine.
              strHostName = DNS.GetHostName ();
              Console.WriteLine ("Local Machine's Host Name: " +  strHostName);
          }
          else
          {
              strHostName = args[0];
          }
          
          // Then using host name, get the IP address list..
          IPHostEntry ipEntry = DNS.GetHostByName (strHostName);
          IPAddress [] addr = ipEntry.AddressList;
          
          for (int i = 0; i < addr.Length; i++)
          {
              Console.WriteLine ("IP Address {0}: {1} ", i, addr[i].ToString ());
          }
          return 0;
        }    
     }
}

What The Code Does

If you want to obtain the hostname of the local machine, then call the GetHostName method without a parameter. Then use the resulting hostname as a parameter to the GetHostByName method to get the list of IPAddresses that may be associated with the hostname. Then iterate through the collection of addresses to write out the IP Addresses associated with the hostname.

Reminders

Make sure that you include the System.Net namespace in your code; otherwise the compiler will not know where to look for the DNS class. Also when you use VisualStudio.NET for creating the project, make sure that you have the System.NET.Dll in your reference list. For more information on the DNS class and System.Net namespace, please refer to the online documentation for the .NET SDK.