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Lightweight and easy-to-use class library to allow port forwarding in NAT devices with UPNP and/or PMP
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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

How to use?

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

Awesome software using Open.NAT



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.

Here you can see what are the next features to implement. Take it a look!

Build Status

Build status

NuGet version

Version 2.0.16

  • Supports .NET 3.5
  • Fixes defect #28. GetSpecificMappingAsync under LINKSYS WRT1900AC AC1900 fails with 501

Version 2.0.11

  • Allows the creation of mappings with arbitrary Private IP address.
  • Fixes defect #22. Routers failed with 404 when service control url had a question mark (?) - DD-WRT Linux base router (and others probably) fails with 402-InvalidArgument when index is out of range. - Some routers retuns invalid mapping entries with empty internal client.

  • Fixes defect #24. GetSpecificMappingEntry fails with 402-InvalidArgument in DD-WRT Linux base router when mapping is not found.

Version 2.0.10

Fixes defect #20. Absolute service control URL path and query miscalculated.

Version 2.0.9

Version 2.0.8

Version 2.0.0

  • Thus version breaks backward compatibility with v1.
  • Changes the event-based nature of discovery to an asynchronous one.
  • Managed port mapping timelife.

Version 1.1.0

  • Fix for SSDP Location header.
  • After this version Open.NAT breaks backward compatibility.

Version 1.0.19

  • Minor changes previous to v2.

Version 1.0.18

  • Discovery timeout raises an event.
  • Permanent mappings are created when NAT only supports that kind of mappings.
  • Protocol to use in discovery process can be specified.
  • Automatic renew port mappings before expiration.
  • Add operations timeout after 4 seconds.
  • Add parameters validation in Mapping class.
  • Fix UnhandledException event was never raised.

Version 1.0.17

  • Discovery timeout added.
  • Auto release ports opened in the session.
  • Fix NextSearch to use UtcNow (also performance)
  • Fix LocalIP property after add a port.
  • Tracing improvements

Version 1.0.16

  • Discovery performance and bandwidth improved
  • Tracing improved
  • Cleaner code

Help me to maintain Open.NAT

Bitcoin address


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