Keep Port Open

[Josh Glottmann]

I'm on a university WiFi network and as a result, I have to consistently (every 20-60 seconds) tap my PTT in order to keep the voice port open. If I don't do this, I cannot hear pilots on the frequency when I'm controlling.
I know others have experienced this issue in the past and I'm wondering what the best solution may be. I'm not sure if my university would be able to open ports for me.

Is there any application which may be able to send a small packet every few seconds in order to keep the port open? Any other suggestions on how to resolve this?

[Toby Rice]

I had this same problem. Never was able to fix it. I’ve moved since then.

It’s super annoying.... I feel your pain. I’d be interested to know if anyone else knows a fix?

[Meg Bruck]

Other than hitting the PTT key every 2 minutes...

No.

[Mark Hubbert]

Is the issue related to your internet or is it a software thing?  I have the same issues and it seems to be centered around VRC.  I do not have these issues with the pilot clients.  Do you experience this with the other ATC clients? 

[Kyle Ekas]

I have also had this issue with VRC in the past, but ever since I forwarded the appropriate ports, have not had any further problems with this. I have had some problems with pilots having the same issue on my frequency as well.

The port not being kept open is kind of a pain, but the only way I know of is to have the port opened on the router or firewall. Try making specific rule sets in the windows firewall settings and see if that helps any.

K

[Josh Glottmann]

When I'm not on university WiFi, the clients work fine. It's the school's end that is causing the problems.
Perhaps someone could make a client to send an empty packet every 5-10 seconds through the ports used for voice.

EDIT: can someone provide me with the ports used for voice comms?

[Meg Bruck]

VRC uses UDP 3290

There are 2 others for vstars but I don't know them off hand. Easy to find with a google search.

[Elai Kindler]

It's weird for me. Some days I have the exact same problem, and some days my VRC doesn't have that problem. I just play luck with it really.

[Kyle Kaestner]

EDIT: can someone provide me with the ports used for voice comms?

Here: http://www1.metacraft.com/VRC/docs/doc.php?page=installing_or_upgrading_vrc

[Ian Cowan]

I used to have the exact same issue, but it seemed to fix itself when we got upgraded internet speed. Wished I knew what the actual fix was because so many people have this issue but I'm not sure.

[Alexandra Robison]

Network Engineer here! I can shed some light on the issue.

VRC uses UDP port 3290 for voice traffic. By definition, UDP traffic is stateless - it does not rely on the 2 parties agreeing on how/when to send it. When a pilot transmits on frequency, the voice server relays that to you as a UDP stream. The problem occurs when your router receives that traffic and does not know where to send it (your computer vs your phone vs your smart TV). The reason why keying up every so often alleviates the problem is because your router will track the UDP stream for some period of time (usually 30 seconds to a minute). When you key up, your router keeps track of that connection and while your router is tracking the connection, if it receives the UDP stream from the voice server, it is smart enough to see the two are related and sends it to your computer where VRC gets it. Port forwarding also alleviates the problem because now your router has a permanent rule telling it that ANY UDP data it receives on port 3290, send it to your computer (whether from the voice server or not).

This boils down to the fact that NAT sucks. It is a hack that was implemented to stretch the lifetime of the IPv4 address space. Most of the time, it works great, but things like this show its flaws.

Hope this helps someone understand

[Ryan Savara]

The real question is, can we trick it to keeping the port open with a small and simple lightweight application that sends a stream every so often?

[Josh Glottmann]

This boils down to the fact that NAT sucks. It is a hack that was implemented to stretch the lifetime of the IPv4 address space. Most of the time, it works great, but things like this show its flaws.

Thanks for the input, do you have any recommendation?

[Kyle Ekas]

This boils down to the fact that NAT sucks. It is a hack that was implemented to stretch the lifetime of the IPv4 address space. Most of the time, it works great, but things like this show its flaws.

Hope this helps someone understand

Super interesting post.

[Daniel Hawton]

The real question is, can we trick it to keeping the port open with a small and simple lightweight application that sends a stream every so often?

No. Operating systems don't allow two applications to bind to the same UDP port.  The easiest method is to port forward or be directly connected to the modem.  There is not a way to have a small application sit and send blank packages over a port bound by vPilot, VRC, vSTARS, vERAM, etc. Windows, Linux, Mac OS, etc. will refuse the connection identifying that the port is already in use.