What is a simple STUN test I can perform from a Windows machine?

Question

I want to test whether someone else's Windows machine can access a public STUN service using UDP and receive a response on its network, which I expect is behind a NAT and firewall. I do not have physical access to this machine, but I know someone who will. I expect that no development environment will be available, so I doubt I can supply code to run other than by web browser.

Is there a simple Windows utility that I can use to check whether a UDP STUN request succeeds? Or is there a website that will get a browser to perform a UDP-based STUN request?

My best current solution is to use an end-to-end UDP based service requiring STUN like talky.io in a web browser. This has several other complicating factors like requiring audio and video capture, so I would prefer a simpler test.

Solution

The official WebRTC "testrtc" project has a module which does this.

You can see it live at https://test.webrtc.org/.