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So I'm going out of my mind trying to figure this out and I feel like it's either going to be a really simple fix or something wrong with the router.

I'm trying to forward a UDP port to a program running on Server 2012 R2 which is on a vSphere machine.

I'm able to successfully forward TCP ports (tested with both active programs and a listener). I can even forward the same numbered port in TCP, but it will always fail to open for UDP. (I've set them to all and tested both, and then individually as well)

I have turned off all firewalls (router and machines) and have probably checked my numbers about 7 times.

I've checked what my ISP is blocking for ports and this port is not in the list. I even tried a few other port numbers just for SnG.

I have factory reset and flashed the router.

I've tested the application on my internal network and it works. Switching to external IP to attempt connection is where it fails.

I also had problems with Xbox live a while back, but I chalked it up to it being an Xbox. In retrospect, it was likely the same issue but I wasn't as in depth because, frankly, I didn't care as much.

Any thoughts on where the issue might lie? I feel like with it being so specific to just UDP that I'm just missing a setting somewhere, but you would think that manually forwarding a port would be enough, which makes me think there's a bigger problem. And of course googling and searching forums just leads to instructions on how to port forward, leaving me even more frustrated.

Thanks for any help you can give!