/Sarnata.Net.BareFtp/Protocol/HostNameResolver.cs

// HostNameResolver.cs
// 
// Modified slightly for bareFTP by Christian Eide <christian@bareftp.org>
//
// Original copyright notice:
// -------------------
// 
// Copyright (C) 2004 Enterprise Distributed Technologies Ltd

// 

// www.enterprisedt.com

// 

// This library is free software; you can redistribute it and/or

// modify it under the terms of the GNU Lesser General Public

// License as published by the Free Software Foundation; either

// version 2.1 of the License, or (at your option) any later version.

// 

// This library is distributed in the hope that it will be useful,

// but WITHOUT ANY WARRANTY; without even the implied warranty of

// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

// Lesser General Public License for more details.

// 

// You should have received a copy of the GNU Lesser General Public

// License along with this library; if not, write to the Free Software

// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

using System;

using System.Net;

using System.Net.Sockets;

using System.Text.RegularExpressions;



namespace Sarnata.Net.BareFtp.Protocol
{
		
	public class HostNameResolver

    {

        private const string IP_ADDRESS_REGEX = @"[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}";



        public static IPAddress GetAddress(string hostName)

        {

            if (hostName == null)

                throw new ArgumentNullException();

            IPAddress address = null;

            if (Regex.IsMatch(hostName, IP_ADDRESS_REGEX))

                address = IPAddress.Parse(hostName);

            else

            {

                IPAddress[] addresses = Dns.GetHostEntry(hostName).AddressList;

                // see if there's an IPv4 address

                foreach (IPAddress a in addresses)

                    if (a.AddressFamily == System.Net.Sockets.AddressFamily.InterNetwork)

                        address = a;

                // otherwise throw an exception coz we don't handle IPv6 yet.

                if (address == null)

                    throw new ArgumentException(hostName + " resolves to an unsupported protocol.");

			}

            return address;

        }

    }
}