GameServerManagers / GameServerManagers/LinuxGSM

[Bug]: Cannot query lgsm server when crossplay is enabled (a2s_info won't connect)

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#4,888 opened on Mar 23, 2026 1 comment 0 reactions 0 assignees View on GitHub

command: details command: monitor distro: Ubuntu engine: unity3d game: Valheim info: query type: bug

Dominant language: Shell
Stars: 4.9k
Forks: 864
PR merge metrics: No merged PRs in 30d

Description

### User story

As a dedicated server host, using cloud service providers, I want to be able to query my lgsm server so that I can automate server operations (startup / shutdown).

### Game

Valheim

### Linux distro

Ubuntu 24.04

### Command

command: details, command: monitor

### Further information

## Context

I've been hosting a [Valheim Server](https://linuxgsm.com/servers/vhserver/) for a group of friends off-and-on for several years. The game server is VM on GCP -- it starts `lgsm` / `vhserver` as soon as it boots. Then I built a discord bot that listens in our discord, and can turn the VM off/on using pub/sub messages attached to a "Cloud Function."

My Discord bot uses [Steam's a2s_info query](https://developer.valvesoftware.com/wiki/Server_queries) to determine if the server is up, and if so, state how many people are logged in. It uses the a2s_info query to tell people when the server is up (e.g. "*Starting.... Started!*"), so it's an important part of my setup.

## Problem

When crossplay is enabled, Steam's server queries are broken (e.g. A2S_info, A2S_ping).

At first I thought this was a port forwarding issue, but I think there's a more significant reason why this doesn't work. Specifically, when crossplay is enabled, queries are broken *on the host itself*.

With Crossplay Turned on.
```
$ ./vhserver start
$ echo -n -e "\xff\xff\xff\xff\x54\x53\x6f\x75\x72\x63\x65\x20\x45\x6e\x67\x69\x6e\x65\x20\x51\x75\x65\x72\x79\x00" | nc -u 127.0.0.1 2457

```

With Crossplay Turned off:
```
$ ./vhserver start
$ echo -n -e "\xff\xff\xff\xff\x54\x53\x6f\x75\x72\x63\x65\x20\x45\x6e\x67\x69\x6e\x65\x20\x51\x75\x65\x72\x79\x00" | nc -u 127.0.0.1 2457
I$servername$$servername$valheim
dl1.0.0.0 ̧8@g=0.221.12,n=36,m=*
```

Prior Issue: https://github.com/GameServerManagers/LinuxGSM/issues/4748

## Expected Behavior

Whether crossplay is enabled or not:

1. Players can join the game via the Valheim game client.
2. a2s_info server queries return server information.

## Game Startup

### With Crossplay

`./valheim_server.x86_64 -name $servername -password $passwd -port 2456 -world $worldname -public 1 -savedir '/home/vhserver/.config/unity3d/IronGate/Valheim' -saveinterval 1800 -backups 4 -backupshort 7200 -backuplong 43200 -crossplay -instanceid 1`

### Without Crossplay

## Server Query

There are several ways to query a server.

* URL, using the Steam API: https://api.steampowered.com/ISteamApps/GetServersAtAddress/v0001?addr=$ip_addr
* **Note**: Replace $ip_addr with the public-facing IP of the game server.
* If successful the `servers:` list in the reply will not be empty.
* CLI: On the game server itself, attempt to send the A2S Challenge: `echo -n -e "\xff\xff\xff\xff\x54\x53\x6f\x75\x72\x63\x65\x20\x45\x6e\x67\x69\x6e\x65\x20\x51\x75\x65\x72\x79\x00" | nc -u 127.0.0.1 2457`
* If successful, a chunk of data will be returned on the command line,:

```
I$server_name$valheim
^C1.0.0.0 8@g=0.221.12,n=36,m=*
```

If run from a remote host, the steam game server could issue a challenge, which looks like several random characters in response. Otherwise, a failure looks like *nothing* happens.

## Network Setup

### IP

The game server, hosted on GCP, has a static, publicly routable IP. It's pingable from my home workstation as well as from another VM.

### Firewall

I've opened the following ports (ingress) from 0.0.0.0/0:

tcp:
2456-2458,
27015-27030,
27036-27037

udp:
2456-2458,
4380,
27000-27031,
27036

### Relevant log output

```shell
### Without Crossplay Enabled ###

$ ./vhserver dt

Distro Details
================================================================================================================
Date: Mon Mar 23 04:13:49 UTC 2026
Distro: Debian GNU/Linux 13 (trixie)
Arch: x86_64
Kernel: 6.12.73+deb13-cloud-amd64
Hostname: instance-20260322-040156
Environment: google
Uptime: 0d, 1h, 39m
tmux: 3.5a
glibc: 2.41

Server Resource
================================================================================================================
CPU
Model: AMD EPYC 7B13
Cores: 2
Frequency: 2449.998MHz
Avg Load: 0.14, 0.03, 0.01

Memory
Mem: total used free cached available
Physical: 7.8GB 1.3GB 6.4GB 866MB 6.4GB
Swap: 0B 0B 0B

Storage
Filesystem: /dev/sda1
Total: 9.7G
Used: 5.2G
Available: 4.0G

Network
IP: 0.0.0.0
Internet IP: 34.42.187.172

Valheim Resource Usage
================================================================================================================
CPU Used: 64.1%
Mem Used: 13.4% 1065MB

Storage
Total: 1.9G
Serverfiles: 1.7G

Valheim Server Details
================================================================================================================
Server name: $servername
App ID: 896660
Server IP: 0.0.0.0:2456
Internet IP: 34.42.187.172:2456
Server password: $passwd
Save interval: 1800s
Master server: not listed
Status: STARTED

vhserver Script Details
================================================================================================================
Script name: vhserver
LinuxGSM version: v25.2.0
glibc required: 2.15
IFTTT alert: off
Update on start: off
User: vhserver
Location: /home/vhserver

Backups
================================================================================================================
No Backups created

Command-line Parameters
================================================================================================================
./valheim_server.x86_64 -name $servername -password $passwd -port 2456 -world $worldname -public 1 -savedir '/home/vhserver/.config/unity3d/IronGate/Valheim' -saveinterval 1800 -backups 4 -backupshort 7200 -backuplong 43200 -instanceid 1

Ports
================================================================================================================
Change ports by editing the parameters in:
/home/vhserver/lgsm/config-lgsm/vhserver

Useful port diagnostic command:
ss -tuplwn | grep valheim_server.

DESCRIPTION PORT PROTOCOL LISTEN
Game 2456 udp 0
Query 2457 udp 1

Status: STARTED

core_exit.sh exiting with code: 0

$ ./vhserver qr

Valheim Developer Query Raw
=================================

IP Addresses Variables
=================================

IP: 0.0.0.0
HTTP IP: 10.128.0.4
Public IP: 35.208.212.176
Telnet IP: 10.128.0.4
Display IP:

Query IP Addresses
=================================

127.0.0.1
10.128.0.4
35.208.212.176

Game Server Ports
=================================
Port Name Port Number Status TCP UDP
Game: 2456 0
Query: 2457 1 UNCONN
API:
App:
BattleEye:
Beacon:
ReliableMessaging:
Client:
File:
HTTP:
HTTP Query:
Web Interface:
Game: Master:
RAW UDP Socket:
RCON:
Steam:
Steamworks P2P:
Steam: Auth:
Telnet:
Stats:
SourceTV:
UDP Link:
Voice:
Voice (Unused):

SS Output
=================================
Useful port diagnostic command:
ss -tuplwn | grep valheim_server.

udp UNCONN 0 0 0.0.0.0:2457 0.0.0.0:* users:(("valheim_server.",pid=37871,fd=36))
udp UNCONN 0 0 0.0.0.0:36565 0.0.0.0:* users:(("valheim_server.",pid=37871,fd=50))
udp UNCONN 0 0 *:47464 *:* users:(("valheim_server.",pid=37871,fd=35))
tcp LISTEN 0 128 127.0.0.1:39921 0.0.0.0:* users:(("valheim_server.",pid=37871,fd=32))

Query Port (2457) - Gamedig Output
=================================

PORT: 2456
QUERY PORT: 2457

Is My Game Server Online?
=================================
Game server status: https://ismygameserver.online//35.208.212.176:2457

Gamedig Raw Output
=================================

Failure! gamedig not installed

Query Port (2457) - gsquery Output
=================================

./query_gsquery.py -a "127.0.0.1" -p "2457" -e ""

usage: usage: python3 query_gsquery.py [options]
query_gsquery.py: error: argument -e/--engine: invalid choice: '' (choose from protocol-valve, protocol-quake2, protocol-quake3, protocol-gamespy1, protocol-unreal2, ut3, minecraft, minecraftbe, jc2m, mumbleping, soldat, teeworlds)
./query_gsquery.py -a "10.128.0.4" -p "2457" -e ""

Query Port (2457) - TCP Output
=================================

bash -c 'exec 3<> /dev/tcp/'127.0.0.1'/'2457''

bash: connect: Connection refused
bash: line 1: /dev/tcp/127.0.0.1/2457: Connection refused

TCP query FAIL
bash -c 'exec 3<> /dev/tcp/'10.128.0.4'/'2457''

bash: connect: Connection refused
bash: line 1: /dev/tcp/10.128.0.4/2457: Connection refused

TCP query FAIL
bash -c 'exec 3<> /dev/tcp/'35.208.212.176'/'2457''

bash: connect: Connection refused
bash: line 1: /dev/tcp/35.208.212.176/2457: Connection refused

TCP query FAIL

Game Port (2456) - TCP Output
=================================

TCP Raw Output
=================================

bash -c 'exec 3<> /dev/tcp/'127.0.0.1'/'2456''

bash: connect: Connection refused
bash: line 1: /dev/tcp/127.0.0.1/2456: Connection refused

TCP query FAIL
bash -c 'exec 3<> /dev/tcp/'10.128.0.4'/'2456''

bash: connect: Connection refused
bash: line 1: /dev/tcp/10.128.0.4/2456: Connection refused

TCP query FAIL
bash -c 'exec 3<> /dev/tcp/'35.208.212.176'/'2456''

bash: connect: Connection refused
bash: line 1: /dev/tcp/35.208.212.176/2456: Connection refused

TCP query FAIL

Steam Master Server Response
=================================

curl -m 3 -s https://api.steampowered.com/ISteamApps/GetServersAtAddress/v0001?addr=35.208.212.176

Response: false

core_exit.sh exiting with code: 0

### With Crossplay Enabled ###

vhserver@instance-20260322-040156:~$ ./vhserver dt

Distro Details
================================================================================================================
Date: Mon Mar 23 04:59:58 UTC 2026
Distro: Debian GNU/Linux 13 (trixie)
Arch: x86_64
Kernel: 6.12.73+deb13-cloud-amd64
Hostname: instance-20260322-040156
Environment: google
Uptime: 0d, 2h, 25m
tmux: 3.5a
glibc: 2.41

Memory
Mem: total used free cached available
Physical: 7.8GB 1.2GB 6.4GB 910MB 6.4GB
Swap: 0B 0B 0B

Storage
Filesystem: /dev/sda1
Total: 9.7G
Used: 5.3G
Available: 4.0G

Network
IP: 0.0.0.0
Internet IP: 35.208.212.176

Valheim Resource Usage
================================================================================================================
CPU Used: 65.3%
Mem Used: 11.6% 924MB

Storage
Total: 1.9G
Serverfiles: 1.7G

Valheim Server Details
================================================================================================================
Server name: $servername
App ID: 896660
Server IP: 0.0.0.0:2456
Internet IP: 35.208.212.176:2456
Server password: #passwd
Save interval: 1800s
Master server: not listed
Status: STARTED

Backups
================================================================================================================
No Backups created

Command-line Parameters
================================================================================================================
./valheim_server.x86_64 -name $servername -password $passwd -port 2456 -world #worldname -public 1 -savedir '/home/vhserver/.config/unity3d/IronGate/Valheim' -saveinterval 1800 -backups 4 -backupshort 7200 -backuplong 43200 -crossplay -instanceid 1

Useful port diagnostic command:
ss -tuplwn | grep valheim_server.

DESCRIPTION PORT PROTOCOL LISTEN
Game 2456 udp 0
Query 2457 udp 0

Status: STARTED

core_exit.sh exiting with code: 0

vhserver@instance-20260322-040156:~$ ./vhserver qr

Valheim Developer Query Raw
=================================

IP Addresses Variables
=================================

IP: 0.0.0.0
HTTP IP: 10.128.0.4
Public IP: 35.208.212.176
Telnet IP: 10.128.0.4
Display IP:

Query IP Addresses
=================================

127.0.0.1
10.128.0.4
35.208.212.176

SS Output
=================================
Useful port diagnostic command:
ss -tuplwn | grep valheim_server.

udp UNCONN 6400 0 0.0.0.0:2457 0.0.0.0:* users:(("valheim_server.",pid=40717,fd=46))
udp UNCONN 0 0 0.0.0.0:51794 0.0.0.0:* users:(("valheim_server.",pid=40717,fd=52))
udp UNCONN 0 0 *:35262 *:* users:(("valheim_server.",pid=40717,fd=45))
tcp LISTEN 0 128 127.0.0.1:34247 0.0.0.0:* users:(("valheim_server.",pid=40717,fd=33))

Query Port (2457) - Gamedig Output
=================================

PORT: 2456
QUERY PORT: 2457

Is My Game Server Online?
=================================
Game server status: https://ismygameserver.online//35.208.212.176:2457

Gamedig Raw Output
=================================

Failure! gamedig not installed

Query Port (2457) - gsquery Output
=================================

./query_gsquery.py -a "127.0.0.1" -p "2457" -e ""

Query Port (2457) - TCP Output
=================================

bash -c 'exec 3<> /dev/tcp/'127.0.0.1'/'2457''

bash: connect: Connection refused
bash: line 1: /dev/tcp/127.0.0.1/2457: Connection refused

TCP query FAIL
bash -c 'exec 3<> /dev/tcp/'10.128.0.4'/'2457''

bash: connect: Connection refused
bash: line 1: /dev/tcp/10.128.0.4/2457: Connection refused

TCP query FAIL
bash -c 'exec 3<> /dev/tcp/'35.208.212.176'/'2457''

bash: connect: Connection refused
bash: line 1: /dev/tcp/35.208.212.176/2457: Connection refused

TCP query FAIL

Game Port (2456) - TCP Output
=================================

TCP Raw Output
=================================

bash -c 'exec 3<> /dev/tcp/'127.0.0.1'/'2456''

bash: connect: Connection refused
bash: line 1: /dev/tcp/127.0.0.1/2456: Connection refused

TCP query FAIL
bash -c 'exec 3<> /dev/tcp/'10.128.0.4'/'2456''

bash: connect: Connection refused
bash: line 1: /dev/tcp/10.128.0.4/2456: Connection refused

TCP query FAIL
bash -c 'exec 3<> /dev/tcp/'35.208.212.176'/'2456''

bash: connect: Connection refused
bash: line 1: /dev/tcp/35.208.212.176/2456: Connection refused

TCP query FAIL

Steam Master Server Response
=================================

curl -m 3 -s https://api.steampowered.com/ISteamApps/GetServersAtAddress/v0001?addr=35.208.212.176

Response: false

core_exit.sh exiting with code: 0
```

### Steps to reproduce

1. `./vhserver start`
2. `echo -n -e "\xff\xff\xff\xff\x54\x53\x6f\x75\x72\x63\x65\x20\x45\x6e\x67\x69\x6e\x65\x20\x51\x75\x65\x72\x79\x00" | nc -u 127.0.0.1 2457`

Contributor guide

Open the contributing guide

Research direction

No LinuxGSM file or test is identified in the report. Start by reproducing the comparison with ./vhserver start, the documented nc A2S query, and the ./vhserver dt and qr diagnostics with crossplay enabled and disabled. Done means identifying a LinuxGSM-side change, if one is supported, that restores the expected query behavior.

Written by the indexing model from the issue text.

Assessment

Tech stack: bash, linux
Domain: cli, devops
Issue type: Bug
Difficulty: 4/5
Estimated time: 3-5 days
Activity status: Quiet
Clarity: Needs clarification
Newbie friendliness: 35/100

[Bug]: Cannot query lgsm server when crossplay is enabled (a2s_info won't connect)

Description

Contributor guide

Research direction

Assessment

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