How to make port forwarding with UPNPNATClass
<p>I' trying to do port forwarding. I've done following:</p>

<p>NATUPNPLib.dll was added to references 
NATUPNPLib was added to using section of page
Following codes were written
But a null reference exception thrown</p>

<pre><code>using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Data.SqlClient;
using System.Net.Sockets;
using System.Net;
using NATUPNPLib;

namespace ConsoleApplication4
{
    class Program
    {
        static void Main(string[] args)
        {
            UPnPNATClass upnpnat = new UPnPNATClass();
            IStaticPortMappingCollection mappings = upnpnat.StaticPortMappingCollection;
            foreach (IStaticPortMapping map in mappings)
            {
                Console.WriteLine(map.ExternalIPAddress);
            }


            Console.ReadKey();
        }
    }
}
</code></pre>

<p>How can I overcome this problem?</p>
