Simple NSLookUp Implementation in C#

This is code implementation for simple nslookup. As you can see from the code listing, I've used classes defined in the System.Net namespace. You must have to add reference to this namespace before you use any of this namespace classes.

I've used IPHostEntry, Dns, IPEntry and other classes. See attached code for more details.

using System;
using System.Net;
namespace nslookup
{
/// <summary>
///
/// <title>nslookup</title>
/// <description>
/// *nix simple nslookup clone for the Win32 platform (Console Application)
/// Does A DNS lookup by Host Name or IP. Host Name lookups can return
/// multiple IP Ranges.
/// </description>
/// <author>Doug Bell</author>
/// <version>1.0</version>
/// <date>March 23 2002</date>
///
/// </summary>
class NSLookup
{
/// <summary>
///
/// <description>Application entry point.</description>
/// <param name="args">Host Address, IP Address or -help command line
options
</param>
/// <return>int Return code 0 for success -1 for failure or error</return>
///
/// </summary>
[STAThread]
static int Main(string[] args)
{
//Make sure we were passed something, otherwise return help.
if (args.Length < 1 || args[0].Equals("-help"))
{
Console.WriteLine("Usage is: nslookup [Host Name] | [Host IP] | -help");
Console.WriteLine("nslookup foo.bar.com (Returns IP Address for Host Name)");
Console.WriteLine("nslookup 123.123.123.123 (Returns Host Name for Address)");
Console.WriteLine("nslookup -help (Returns this Help Message)");
return -1;
}
else
{
//We have something, try to look it up....
try
{
//The IP or Host Entry to lookup
IPHostEntry ipEntry;
//The IP Address Array. Holds an array of resolved Host Names.
IPAddress [] ipAddr;
//Value of alpha characters
char[] alpha = "aAbBcCdDeEfFgGhHiIjJkKlLmMnNoOpPqQrRsStTuUvVwWxXyYzZ-".ToCharArray();
//If alpha characters exist we know we are doing a forward lookup
if (args[0].IndexOfAny(alpha) != -1)
{
ipEntry = Dns.GetHostByName (args[0]);
ipAddr = ipEntry.AddressList;
Console.WriteLine("\nHost Name : " + args[0]);
int i = 0;
int len = ipAddr.Length;
for (i = 0; i < len; i++)
{
Console.WriteLine ("Address {0} : {1} ", i, ipAddr[i].ToString ());
}
return 0;
}
//If no alpha characters exist we do a reverse lookup
else
{
ipEntry = Dns.Resolve(args[0]);
Console.WriteLine("Address : " + args[0]);
Console.WriteLine("Host Name : " + ipEntry.HostName);
return 0;
}
}
catch(System.Net.Sockets.SocketException se)
{
// The system had problems resolving the address passed
Console.WriteLine(se.Message.ToString());
return -1;
}
catch(System.FormatException fe)
{
// Non unicode chars were probably passed
Console.WriteLine(fe.Message.ToString());
return -1;
}
}
}
//End Main(string[])
}//End NSLookup Class
}//End nslookup namespace