Open.NAT is a lightweight and easy-to-use class library to allow port forwarding in NAT devices that support UPNP (Universal Plug & Play) and/or PMP (Port Mapping Protocol).

NATed computers cannot be reached from outside and this is particularly painful for peer-to-peer or friend-to-friend software. The main goal is to simplify communication amoung computers behind NAT devices that support UPNP and/or PMP providing a clean and easy interface to get the external IP address and map ports and helping you to achieve peer-to-peer communication.

• Tested with .NET YES
• Tested with Mono YES

With nuget :

Install-Package Open.NAT

Go on the nuget website for more information.

The simplest scenario:

var discoverer = new NatDiscoverer();
var device = await discoverer.DiscoverDeviceAsync();
var ip = await device.GetExternalIPAsync();
Console.WriteLine("The external IP Address is: {0} ", ip);

The following piece of code shows a common scenario: It starts the discovery process for a NAT-UPNP device and onces discovered it creates a port mapping. If no device is found before ten seconds, it fails with NatDeviceNotFoundException.

var discoverer = new NatDiscoverer();
var cts = new CancellationTokenSource(10000);
var device = await discoverer.DiscoverDeviceAsync(PortMapper.Upnp, cts);

await device.CreatePortMapAsync(new Mapping(Protocol.Tcp, 1600, 1700, "The mapping name"));

For more info please check the Wiki

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• Why Open.NAT? Here you have ten reasons that make Open.NAT a good candidate for you projects
• Visit the Wiki page

Open.NAT is been developed by Lucas Ontivero (@lontivero). You are welcome to contribute code. You can send code both as a patch or a GitHub pull request.