NAT-related disconnection problem/solution

Discussions surrounding the software that lets pilots connect to PilotEdge and the actual simulators

NAT-related disconnection problem/solution

Postby mxasf » Thu Feb 15, 2018 1:17 am

Hi all -
Just documenting a frustrating PilotEdge disconnection problem I troubleshot over the last month or so with Keith Smith. I did eventually come up with a solution, and wanted to make it public.

I am running Pilotedge on Linux or Windows XPlane v10 or v11. (although the OS or XP version # is irrelevant). The system is a home desktop that connects to an Asus wireless router / AT&T internet modem. The router uses "Advanced Tomato" custom firmware (newest version v3.5-140).

The symptom was that I could connect to Pilotedge fine, and usually get 5 or 10 minutes of function: file an IFR flight plan, copy it back, get a ground clearance, and around takeoff I would be abruptly disconnected. Upon Keith's recommendation, I started looking at the bottom of the "Pilotedge_out.txt" file (in the XP folder). It is a great resource to troubleshoot connection problems. There are a number of entries "received malformed vx update" which are not considered problematic. (and probably occur for many users).

But for me, prior to disconnection, I invariantly would see an error logged "status = 253" and then some various disconnection messages.

Looking at earlier forum posts here, my first thought was that I needed to port-forward from the router to my desktop (UDP 9986; TCP 5558). I tried this, but the problem continued to occur.

In desperation, and after looking at additional forums (Vatsim/XSquawkbox etc), I saw some users note issues with "NAT" settings in the router (Network Access Translation).
This indeed appeared to be the problem for me, possibly caused by a recent router firmware update, and maybe to boost security.

Ultimately what completely fixed the disconnection problem for me was two settings (Advanced Settings Menu --> Firewall):
NAT Loopback: was "all" --> now "forwarded only"
NAT Target: was "Masquerade" ---> now "SNAT".
After doing both things, the port forwarding described above also became un-necessary, and could be disabled. (i.e. the problem was specifically the NAT settings, and not port forwarding).

Hopefully this helps some people, particularly weirdos like myself that insist on custom router firmwares. "Advanced Tomato" really is an amazing router firmware IMO.
As routers improve their security, I could imagine NAT settings problems pop up for more PilotEdgers.

good luck and thanks to Keith for helping me get through this.
Posts: 1
Joined: Thu Feb 15, 2018 12:21 am

Re: NAT-related disconnection problem/solution

Postby Keith Smith » Wed Feb 21, 2018 2:42 pm

As someone who was, at one time, pretty good at TCP/IP networking, this one was baffling for me. Hats off to mxasf for being able to resolve this one. And, here's to hoping that nobody else is running customer router firmware :)
Keith Smith
Posts: 9800
Joined: Sat Oct 09, 2010 8:38 pm
Location: Pompton Plains, NJ

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