Port Mapping in C# is not working

Question

i need to perform port forwarding in a desktop application written in C#

i used this code :

using System;
using System.Threading;
using NATUPNPLib;

namespace iSpyApplication
{
    public static class NATControl
    {
        public static UPnPNAT NAT = new UPnPNAT();
        private static IStaticPortMappingCollection _mappings;

        public static IStaticPortMappingCollection Mappings
        {
            get
            {
               if (_mappings==null)
               {

                   try
                   {
                       if (NAT.NATEventManager != null)
                        _mappings = NAT.StaticPortMappingCollection;
                   }
                   catch
                   {
                   }
               }

               return _mappings;
            }
         }

        public static bool SetPorts(int wanPort, int lanPort)
        {
           bool b = false;
           int i = 3;
           while (Mappings == null && i > 0)
           {
               Thread.Sleep(2000);
               i--;
           }

           if (Mappings != null)
           {
               try
               {
                   Mappings.Remove(wanPort, "TCP");
               }
               catch (Exception ex)
               {
                   // do something
               }
               try
               {
                   Mappings.Add(wanPort, "TCP", lanPort, internalIP, true, "iSpy");
                   b = true;
               }
               catch (Exception ex)
               {
                   // do something
               }
           }

           return b;

        } // method

  } // class    

} // namespace

UPnP is enabled in my linksys router

the code is running and not giving any errors or exceptions, however, mapping is simply not happening.

here is how i am testing it:

1. i have an application that listens to an internal port e.g. 8080.

2. i manually add a mapping entry to my router:

   application : HTTP , external port 8080 , internal port 8080, protocol: TCP , internal IP , enabled

3. i request the following URL in my browser: http : // publicIP : externalport /

4. the application receives a socket on the internal port and replies with a message.

i remove the mapping entry and try to add it programmatically

1. the same
2. i run a code that performs mapping
3. the same

4. browser displays the followin message :

   Unable to connect

   Firefox can't establish a connection to the server at publicIP:externalPort

i have searched for C# code that performs mapping, and they all look the same. Why would mapping fail ? Thanks in advance

Answer 1

Idea 1: IStaticPortMappingCollection.Add does have a return value, which you should check for errors.

Idea 2: Your router may not allow you setting a static route over UPnP.

Run DeviceSpy from UPnP Developer Tools and look for your router. Its URN ends in *:InternetGatewayDevice. Under the device, look for service WANIPConnection. Look for the number after the service name. If it is 2, then you are out of luck. WANIPConnection service description (downloadable at the UPnP website) states at the PortMappingLeaseDuration:

In release 1.0, a value of 0 was used to create a static port mapping. In version 2.0, it is no longer possible to create static port mappings via UPnP actions. Instead, an out-of-band mechanism is REQUIRED to do so (cf. WWW-administration, remote management or local management).

Even if your WANIPConnection is still version 1, you can use DeviceSpy for finding out whether the route is really being set by your code or not.