Simple Voice Chat not working

[ThomasTricot]

Describe the problem

I am running a Minecraft server inside Docker on Windows (Docker Desktop).
The server works correctly over TCP (port 25565), and it is reachable both via localhost and the LAN IP.
The Simple Voice Chat mod starts correctly and listens on UDP port 24454 inside the container.
The port is exposed in Docker (24454:24454/udp), allowed in the Windows firewall, and confirmed as listening with netstat.
However, clients cannot connect to the voice chat server.
The /voicechat test <player> command returns "Client not connected".

FYI:

• I didn't change anything on the data\config\voicechat\voicechat-server.properties file (I tried many things in there but nothing works).
• It's seem there is an issue with the docker network because when I put in the address server "127.0.0.1" I have a timeout. Only puting "localhost" as the server address let me in.
• I firstly talk with the official dev of the Simple Voice Mod (Max Henkel), but we came to the conclusion that the problem was caused by Docker and not by the mode itself.

Container definition

services:
  mc:
    container_name: minecraft-test-voice-chat
    image: itzg/minecraft-server:latest
    ports:
      - "25565:25565"
      - "24454:24454/udp"
    environment:
      EULA: "TRUE"
      DIFFICULTY: "hard"

      # Mandatory
      CF_API_KEY: ${CF_API_KEY}
      MODPACK_PLATFORM: AUTO_CURSEFORGE
      CF_MODPACK_ZIP: /modpacks/toto.zip
      CF_SLUG: "custom"

      # Memory
      MEMORY: 8G
      JVM_OPTS: "-Xms6G -Xmx8G"
    volumes:
      - ./data:/data
      - ./modpacks:/modpacks:ro

Container logs

[init] Changing ownership of /data to 1000 ...
[init] Running as uid=1000 gid=1000 with /data as 'drwxrwxrwx 1 1000 1000 4096 Jan 15 20:02 /data'
[init] Image info: buildtime=2026-01-13T02:57:01.149Z,version=java25,revision=0a98bee40ea9b86500ea7b6611784902a553803f
[mc-image-helper] 20:03:01.824 INFO  : Installing modpack 'toto' version  from provided modpack zip
[mc-image-helper] 20:03:07.203 INFO  : Downloaded mod file mods/voicechat-neoforge-1.21.1-2.6.11.jar
[mc-image-helper] 20:03:08.668 INFO  : Running NeoForge 21.1.215 installer for Minecraft 1.21.1. This might take a while...
[init] Copying any mods from /mods to /data/mods
[init] Copying any configs from /config to /data/config
[init] Creating server properties in /data/server.properties
[init] Disabling whitelist functionality
[mc-image-helper] 20:07:08.519 INFO  : Created/updated 6 properties in /data/server.properties
[init] Using server icon from https://m.media-amazon.com/images/I/41zjIUAoLBL._UX358_FMwebp_QL85_.jpg...
[init] Converting image to 64x64 PNG...
[init] Setting initial memory to 8G and max to 8G
[init] Using Forge supplied run.sh script...
WARNING: A terminally deprecated method in sun.misc.Unsafe has been called
WARNING: sun.misc.Unsafe::objectFieldOffset has been called by cpw.mods.jarhandling.impl.SecureJarVerifier$UnsafeAccessor (file:/data/libraries/cpw/mods/securejarhandler/3.0.8/securejarhandler-3.0.8.jar)
WARNING: Please consider reporting this to the maintainers of class cpw.mods.jarhandling.impl.SecureJarVerifier$UnsafeAccessor
WARNING: sun.misc.Unsafe::objectFieldOffset will be removed in a future release
[20:07:15.432] [main/INFO] [loading.moddiscovery.ModDiscoverer/SCAN]: Found mod file "voicechat-neoforge-1.21.1-2.6.11.jar" [locator: {mods folder locator at /data/mods}, reader: mod manifest] 
[20:07:15.723] [main/INFO] [loading.moddiscovery.locators.JarInJarDependencyLocator/]: Found 2 dependencies adding them to mods collection 
[20:07:15.724] [main/INFO] [loading.moddiscovery.ModDiscoverer/SCAN]: Found gamelibrary file "mixinextras-neoforge-0.5.0.jar" [parent: neoforge-21.1.215-universal.jar, locator: jarinjar, reader: mod manifest] 
[20:07:15.725] [main/INFO] [loading.moddiscovery.ModDiscoverer/SCAN]: Found library file "net.neoforged.neoforge-coremods-21.1.215.jar" [parent: neoforge-21.1.215-universal.jar, locator: jarinjar, reader: mod manifest] 
[20:07:15.726] [main/INFO] [loading.moddiscovery.ModDiscoverer/]: 
     Mod List:
		Name Version (Mod Id)
		Minecraft 1.21.1 (minecraft)
		NeoForge 21.1.215 (neoforge)
		Simple Voice Chat 1.21.1-2.6.11 (voicechat) 
[20:07:16.229] [main/INFO] [LaunchServiceHandler/MODLAUNCHER]: Launching target 'forgeserver' with arguments [] 
WARN StatusConsoleListener Advanced terminal features are not available in this environment
WARNING: A restricted method in java.lang.System has been called
WARNING: java.lang.System::load has been called by com.sun.jna.Native in module com.sun.jna (union:/data/libraries/net/java/dev/jna/jna/5.14.0/jna-5.14.0.jar%23112!/)
WARNING: Use --enable-native-access=com.sun.jna to avoid a warning for callers in this module
WARNING: Restricted methods will be blocked in a future release unless native access is enabled
[20:07:16] [main/INFO] [MixinExtras|Service/]: Initializing MixinExtras via com.llamalad7.mixinextras.service.MixinExtrasServiceImpl(version=0.5.0).
[20:07:20] [modloading-worker-0/INFO] [ne.ne.ne.co.NeoForgeMod/NEOFORGE-MOD]: NeoForge mod loading, version 21.1.215, for MC 1.21.1
[20:07:21] [modloading-worker-0/INFO] [voicechat/]: [voicechat] Compatibility version 20
[20:07:21] [modloading-worker-0/INFO] [voicechat/]: [voicechat] Loading plugins
[20:07:21] [modloading-worker-0/INFO] [voicechat/]: [voicechat] Loaded 0 plugin(s)
[20:07:21] [modloading-worker-0/INFO] [voicechat/]: [voicechat] Initializing plugins
[20:07:21] [modloading-worker-0/INFO] [voicechat/]: [voicechat] Initialized 0 plugin(s)
[20:07:21] [NeoForge Version Check/INFO] [ne.ne.fm.VersionChecker/]: [voicechat] Starting version check at [https://update.maxhenkel.de/neoforge/voicechat⁠](https://update.maxhenkel.de/neoforge/voicechat)
[20:07:21] [main/INFO] [mojang/YggdrasilAuthenticationService]: Environment: Environment[sessionHost=https://sessionserver.mojang.com, servicesHost=https://api.minecraftservices.com, name=PROD]
[20:07:21] [main/WARN] [minecraft/VanillaPackResourcesBuilder]: Assets URL 'union:/data/libraries/net/minecraft/server/1.21.1-20240808.144430/server-1.21.1-20240808.144430-srg.jar%23118!/assets/.mcassetsroot' uses unexpected schema
[20:07:21] [main/WARN] [minecraft/VanillaPackResourcesBuilder]: Assets URL 'union:/data/libraries/net/minecraft/server/1.21.1-20240808.144430/server-1.21.1-20240808.144430-srg.jar%23118!/data/.mcassetsroot' uses unexpected schema
[20:07:21] [NeoForge Version Check/INFO] [ne.ne.fm.VersionChecker/]: [voicechat] Found status: BETA Current: 1.21.1-2.6.11 Target: 1.21.1-2.6.11
[20:07:21] [main/INFO] [minecraft/Main]: No existing world data, creating new world
[20:07:23] [main/INFO] [minecraft/RecipeManager]: Loaded 1290 recipes
[20:07:23] [main/INFO] [minecraft/AdvancementTree]: Loaded 1399 advancements
[20:07:23] [Server thread/INFO] [minecraft/DedicatedServer]: Starting minecraft server version 1.21.1
[20:07:23] [Server thread/INFO] [minecraft/DedicatedServer]: Loading properties
[20:07:23] [Server thread/INFO] [minecraft/DedicatedServer]: Default game type: SURVIVAL
[20:07:23] [Server thread/INFO] [minecraft/MinecraftServer]: Generating keypair
[20:07:23] [Server thread/INFO] [minecraft/DedicatedServer]: Starting Minecraft server on *:25565
WARNING: A restricted method in java.lang.System has been called
WARNING: java.lang.System::loadLibrary has been called by io.netty.util.internal.NativeLibraryUtil in module io.netty.common (union:/data/libraries/io/netty/netty-common/4.1.97.Final/netty-common-4.1.97.Final.jar%23103!/)
WARNING: Use --enable-native-access=io.netty.common to avoid a warning for callers in this module
WARNING: Restricted methods will be blocked in a future release unless native access is enabled
[20:07:23] [Server thread/INFO] [minecraft/ServerConnectionListener]: Using epoll channel type
[20:07:23] [Server thread/INFO] [minecraft/DedicatedServer]: Preparing level "world"
[20:07:25] [Server thread/INFO] [minecraft/MinecraftServer]: Preparing start region for dimension minecraft:overworld
[20:07:25] [Worker-Main-4/INFO] [minecraft/LoggerChunkProgressListener]: Preparing spawn area: 2%
[20:07:26] [Worker-Main-3/INFO] [minecraft/LoggerChunkProgressListener]: Preparing spawn area: 2%
[20:07:26] [Worker-Main-1/INFO] [minecraft/LoggerChunkProgressListener]: Preparing spawn area: 18%
[20:07:27] [Worker-Main-3/INFO] [minecraft/LoggerChunkProgressListener]: Preparing spawn area: 51%
[20:07:27] [Server thread/INFO] [minecraft/LoggerChunkProgressListener]: Time elapsed: 1678 ms
[20:07:27] [Server thread/INFO] [minecraft/DedicatedServer]: Done (3.652s)! For help, type "help"
[20:07:27] [Server thread/INFO] [minecraft/DedicatedServer]: Starting remote control listener
[20:07:27] [Server thread/INFO] [minecraft/GenericThread]: Thread RCON Listener started
[20:07:27] [Server thread/INFO] [minecraft/RconThread]: RCON running on 0.0.0.0:25575
[20:07:27] [LanServerPinger #1/WARN] [minecraft/LanServerPinger]: LanServerPinger: Network is unreachable
[20:07:27] [Server thread/INFO] [ne.ne.ne.se.pe.PermissionAPI/]: Successfully initialized permission handler neoforge:default_handler
[20:07:27] [VoiceChatServerThread/INFO] [voicechat/]: [voicechat] Voice chat server started at port 24454
[20:10:04] [User Authenticator #1/INFO] [minecraft/ServerLoginPacketListenerImpl]: UUID of player tototricot is 8a1325a1-1bd7-407a-b028-6b946cdda139
[20:10:05] [Server thread/INFO] [minecraft/PlayerList]: tototricot[/172.18.0.1:46384] logged in with entity id 23 at (39.5, 63.0, -1.5)
[20:10:05] [Server thread/INFO] [minecraft/MinecraftServer]: tototricot joined the game
[20:10:05] [Server thread/INFO] [voicechat/]: [voicechat] Received secret request of tototricot (20)
[20:10:05] [Server thread/INFO] [voicechat/]: [voicechat] Sent secret to tototricot
[20:10:05] [VoiceChatPacketProcessingThread/INFO] [voicechat/]: [voicechat] Successfully authenticated player 8a1325a1-1bd7-407a-b028-6b946cdda139
[20:11:48] [Server thread/INFO] [minecraft/MinecraftServer]: [tototricot: Set own game mode to Creative Mode]

[ThomasTricot]

I do still have the icon that's tell me there is a problem:

[itzg]

You seem to have configured everything correctly from a docker perspective. There's not anything I can do to further support this. Please ask around on the Discord server see many people have been able to use Simple Voice Chat.

[rhullah]

I use SVC with this image. You do have to change settings in it's config folder so that clients know where to connect to it. The server side mod communicates with the client side mod in the game to know where to connect to the voice chat server. Since it's running in a container, it thinks it's only available on the container's network. In the config/voicechat/voicechat-server.properties file you need to edit the voice_host value to be the ip/host:port where clients can reach the voice server (so the LAN IP if all players will be on your LAN, or the public IP/host of your server if external players will connect). I have mine set to just the port, 24454, as I think that tells the client to use the same host/ip they used to connect to the server but at the specified port.

The key thing to look at is the Client logs when diagnosing SVC connections. The client logs I'm pretty sure will tell you which host:port it's trying to connect to.

[ThomasTricot]

Thanks @itzg for your response, I didn't find the Discord server that's why I posted an issue, I'll ask around on the server for helps!

Also thanks @rhullah for your response. I do update my voicechat-server.properties with:

bind_address=*
voice_host=24454

but it did'nt work...