"Server offline" for local IP connection, but other players able to join from public

[DarkFlare]

Hi all,

As per title really, I have a DCS server running on a machine locally on Windows Server 2022. Additionally running are DCS SRS and LotATC.

From my PC I am able to connect to the DCS SRS and LotATC instances running on the Windows Server, but attempting to connect to the DCS Server through DCS shows "Server offline".

The server appears in the serverlist (on the DCS website and for other public users). Users connecting via public IP can join, but I am unable to join via local IP, public IP, or hostname.

I have tried disabling the firewall on the Windows Server entirely, there are no blocked packets according to my router firewall (and I would expect not to be able to connect to SRS or LotATC, or RDP for that matter, if traffic was being blocked anyhow), I have disabled IPv6 in the DCS server's autoexec in case that was the issue, but all to no avail.

Anyone else had a similar problem and fixed it?

Cheers

 

[Maverick87Shaka]

it's sound really strange,
We're currently running the same configuration without any issues, it can be related on how your modem/router is trying to route traffic since you have the forwarding rules from WAN to LAN.
But, before investigating further, I'll just make sure this two little things:

• Run the same exact build version between server and client ( Last OB update is 2.7.10.19473 published 07/02/2022 )
• Use the Connect BY IP buttons and type exact server address and port, i.e. 192.168.1.2:10308

 

[DarkFlare]

9 minutes ago, Maverick87Shaka said:

it's sound really strange,
We're currently running the same configuration without any issues, it can be related on how your modem/router is trying to route traffic since you have the forwarding rules from WAN to LAN.
But, before investigating further, I'll just make sure this two little things:

• Run the same exact build version between server and client ( Last OB update is 2.7.10.19473 published 07/02/2022 )
• Use the Connect BY IP buttons and type exact server address and port, i.e. 192.168.1.2:10308

 

Server:

(though interestingly the log file claims 2022-02-08 12:40:33.925 INFO    APP: DCS/2.7.10.19402 (x86_64; Windows NT 10.0.20348))

Client:

 

I've tried to connect via local IP + port, local IP without port, hostname + port, hostname without port, no joy.

I did wonder about routing, but the fact that I can connect to SRS and LotATC on the same machine makes me doubt that that's the issue.

I am also able to telnet to the server from my PC, which results in the following logfile entries:

2022-02-08 13:29:46.171 INFO    NET: accepting connection from [IP]:58122
2022-02-08 13:29:46.174 INFO    NET: adding client[2]
2022-02-08 13:29:48.190 INFO    NET: disconnecting client[2]: Client connect timeout
2022-02-08 13:29:48.206 INFO    NET: remove: client[2]

Though interestingly the IP listed in there is not the IP of my desktop PC, but instead the IP of the gateway that connects the subnet my desktop IP is on to the subnet my server IP is on. Not sure if that would make any difference (and as noted, it doesn't seem to make a difference for SRS or LotATC).

My gut feeling is it's something about the way DCS decides whether a server is up and joinable or not, since routing for other apps seems OK - that's why I tested disabling IPv6 on the autoexec just in case, but no joy.

[Maverick87Shaka]

9 minutes ago, DarkFlare said:

Server:

(though interestingly the log file claims 2022-02-08 12:40:33.925 INFO    APP: DCS/2.7.10.19402 (x86_64; Windows NT 10.0.20348))

My log file is reporting the correct version number, 19473

2022-02-07 19:06:30.265 INFO    APP: DCS/2.7.10.19473 (x86_64; Windows NT 10.0.20348)

And in this particular build there was a netcode change, so the two version will not able to talk to each others.
I'll suggest to try repair/ skatezilla update tools to be sure to bring the client and server at the same exact build version, have the confirmation by the log, and then try again.

[DarkFlare]

7 minutes ago, Maverick87Shaka said:

My log file is reporting the correct version number, 19473

2022-02-07 19:06:30.265 INFO    APP: DCS/2.7.10.19473 (x86_64; Windows NT 10.0.20348)

And in this particular build there was a netcode change, so the two version will not able to talk to each others.
I'll suggest to try repair/ skatezilla update tools to be sure to bring the client and server at the same exact build version, have the confirmation by the log, and then try again.

Yep, that's fixed it. I had re-run the updater twice today and it claimed it was fine both times - I was installing the server for the first time yesterday while the update dropped, it must've gotten out of sync with itself at some point during that. No wonder an hour or two of searching the forums didn't turn up a solution!

In the end I had to re-run the repair twice (after the first time, DCS complained that there were missing files on launch).

Many thanks for the help.

[Maverick87Shaka]

I'm glad that we found the problem source and now everything works as expected!

Fly Safe!
Shaka

 

[zildac]

2 hours ago, DarkFlare said:

Server:

(though interestingly the log file claims 2022-02-08 12:40:33.925 INFO    APP: DCS/2.7.10.19402 (x86_64; Windows NT 10.0.20348))

Client:

 

I've tried to connect via local IP + port, local IP without port, hostname + port, hostname without port, no joy.

I did wonder about routing, but the fact that I can connect to SRS and LotATC on the same machine makes me doubt that that's the issue.

I am also able to telnet to the server from my PC, which results in the following logfile entries:

2022-02-08 13:29:46.171 INFO    NET: accepting connection from [IP]:58122
2022-02-08 13:29:46.174 INFO    NET: adding client[2]
2022-02-08 13:29:48.190 INFO    NET: disconnecting client[2]: Client connect timeout
2022-02-08 13:29:48.206 INFO    NET: remove: client[2]

Though interestingly the IP listed in there is not the IP of my desktop PC, but instead the IP of the gateway that connects the subnet my desktop IP is on to the subnet my server IP is on. Not sure if that would make any difference (and as noted, it doesn't seem to make a difference for SRS or LotATC).

My gut feeling is it's something about the way DCS decides whether a server is up and joinable or not, since routing for other apps seems OK - that's why I tested disabling IPv6 on the autoexec just in case, but no joy.

I suspect that the gateway device that is connecting your Desktop PC network to the network that the DCS server is on is performing HIDE NAT, so in effect your desktop PC appears to have a source IP of the locally attached egress interface of the router that connects both subnets. So that explains that behaviour, and should work fine still. But I can see you’ve got the issue resolved with an update

[cgstever91]

im having a similar issue i can connect if i type in the local ip and port but my local server does not show on the multiplayer screen

i have verified that they are both running the same build version.  

[Maverick87Shaka]

4 hours ago, cgstever91 said:

im having a similar issue i can connect if i type in the local ip and port but my local server does not show on the multiplayer screen

i have verified that they are both running the same build version.  

This is normal behavior on IPv4 and totally expected since on common router setup you'll not be able to use your public IP address to reach out your LAN services, so if you're running server on LAN you'll not be able to see it in the multiplayer list.

[cgstever91]

is there any way to get around that without using a vpn

[Maverick87Shaka]

22 hours ago, cgstever91 said:

is there any way to get around that without using a vpn

Yes, if you connect your flying pc (client) to internet using a VPN you'll be able to see your server in the server list.
Of course it's not at all a recommended connection method since you'll introduce latency, and potentially packet loss ( depending on vpn services )
So it's definitely better to use CONNECT BY IP function for your LAN computer, rather then use a VPN. Maybe it can be used just to check if the server is present after an update or something like that, but really don't see benefits since you can see if the server is up, running DCS version, player count etc... at this link: https://www.digitalcombatsimulator.com/it/personal/server/#allservers

EDIT:
Depending on the router that you have, and normally it's not possible with the "home grade" equipment or ISP provided, you can try to enable what is called "NAT Loopback" instead the common port forwarding that are you using to make server reachable from WAN.
Also popular home premium router like AVM FritzBox has this feature enable only on specific model and firmware version, they like to bring it and out, due to security reason standing at AVM statement.

Edited February 11, 2022 by Maverick87Shaka

[Pocket Kings]

Guys, way too complicated!

From what I've read it's a routing / DNS issue. So, assuming three things that are common (but I'm guessing here):

1.   The server has a FQDN (fully qualified domain name), like myawesomedcsserver.com

2.   The servers' local IP is 192.168.10.100 (adjust to your local subnet please)

3.   The DCS server ports can be reached locally, that's LAN IP Client ---> LAN IP DCS Server instance. I mean why wouldn't they, given there's no firewalling on the WS2022 part? The firewalling takes place at the LAN / WAN gateway (that's the cheap plastic box that's infamously called router, nontheless wrong advertising).

Fix:

- Open up the Windows Editor as Administrator

- Open File ---> C:\Windows\system32\drivers\etc\hosts

- append: 192.168.10.100       myawesomedcsserver.com

- save + close

- cmd.exe

- ping myawesomedcsserver.com

- If you get the reply from your servers' local IP, you've succeeded.

You could also "blackhole" sites like facebook or google with this technique, in fact we did it back in the day when memory was the main constraint.

On the other hand, I could sell you a professional routing and firewall solution like vyOS or pfSense + charge hours for a crap ton of money, but no... not from a fellow DCS pilot. Have a nice weekend!

[QuiGon]

16 hours ago, Pocket Kings said:

1.   The server has a FQDN (fully qualified domain name), like myawesomedcsserver.com

That's common for DCS servers?

[Pocket Kings]

5 hours ago, QuiGon said:

That's common for DCS servers?

It should be, or do you remember IP's by heart? I do, though I work in the field and have a mind map for every octet and every 255 variants (animals to be precise).

BTW, a domain doesn't cost a fortune these days. If you want to cheap out, I'd suggest services like no-ip.com that cost only a registration, but are essentially charge free.

[Maverick87Shaka]

On 2/12/2022 at 10:04 PM, Pocket Kings said:

It should be, or do you remember IP's by heart? I do, though I work in the field and have a mind map for every octet and every 255 variants (animals to be precise).

BTW, a domain doesn't cost a fortune these days. If you want to cheap out, I'd suggest services like no-ip.com that cost only a registration, but are essentially charge free.

No, DCS server doesn't work with FQDN, it works only with your public IP address, so the hosts workaround doesn't help unfortunately.

[Pocket Kings]

Well, then we have to manipulate the routing table. My first thought would be a small virtual machine that acts as a "real" router that runs on top of the Windows Subsystem for Linux. vyOS would be perfect for the job. Alternatively, if available, a Raspberry Pi (any version) could act as a router. If OP tells me his subnet and the local IP of his gateway (the comcast or whatever ISP box) and the local IP of his server, I could write a quick bash script to install and setup this service. As long as his client DCS is pointed at this router, he should be rerouted via the local subnet rather than out to the WAN.

Maybe there's a third resolution: Manipulate the routing table of his Windows 11 client, but I've never done that and I bet it's not persistent across reboots / Windows Updates.

[QuiGon]

On 2/12/2022 at 10:04 PM, Pocket Kings said:

It should be, or do you remember IP's by heart? I do, though I work in the field and have a mind map for every octet and every 255 variants (animals to be precise).

That's not how game servers work.
The game server communicates with EDs master server (if public listing is enabled by the server admin) and EDs master server publishes a list of all those game servers, which you can see in the ingame server browser or here. So you don't need to remember IP addresses (if the server is listed publicly).

Edited February 16, 2022 by QuiGon

[Pocket Kings]

1 hour ago, QuiGon said:

That's not how game servers work like.
The game server communicates with EDs master server (if public listing is enabled by the server admin) and EDs master server publishes a list of all those game servers, which you can see in the ingame server browser or here. So you don't need to remember IP addresses (if the server is listed publicly).

I see, thank you for the clarification.

I guess then OP has to implement my suggested "real" routing solution. There are two ways to go about it:

1. The less intrusive and frankly ugly way, from a network hygiene perspective.

2. The correct and controllable one.

First off, I find those "boxes", one mentioned AVM (and they are the lesser worse ones), hilarious. They cost often times equal as entry level enterprise gear, they try to be a jack of all traits, which opens them up for a truckload of security issues, and they take control away from the user. I believe companies are afraid of the support backlog, if they were to introduce real enterprise features, which by hardware standards these boxes would be very capable of.

Anyhow, here would be the first option (ugly one):

Local DCS Server   -------   Raspberry or virtual router   -------   Switch and other computers   -------   Gateway DHCP etc. (Comcast, whatever whitebox they sent you)   -------   WAN (Internet)

And the cleaner one would be:

Local DCS Server   -------   Swtich and other computers   -------   Raspberry or virtual router as NAT, DHCP, DNS, Firewall  -------   use as modem (Comcast, whatever whitebox they sent you)   -------   WAN (Internet)

Depending on the linespeed of your WAN connection, a Raspberry could be too slow. Alternatively one could also use these smaller low power All-in-one SoC Mainboards. But then we're in the 300$ price range for decent hardware.

Other than that, everything else is rather a hack than a stable solution, like manipulating the routing table within Windows, connecting to a neighbours' WiFi, VPN and so forth.

One more question before I discuss a rather elegant and cost effective idea: Do you plan to let the DCS server run 24/7?

Edited February 16, 2022 by Pocket Kings
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