Server Client Version Mismatch

[Mantaplatte]

Hallo guys, my server says it needs Client Version 1.21.10 but is running in 1.21.11.

Does anyone have an idea how i can fix this.

[init] Running as uid=1000 gid=1000 with /data as 'drwxr-xr-x 11 1000 1000 4096 Feb 2 23:16 /data'
[init] Image info: buildtime=2026-02-04T12:57:41.493Z,version=java25,revision=6bb401f9ff2f98c1925944b546700fca4de73a93
[mc-image-helper] 13:49:03.102 INFO : Processing modpack files for Server 1.0.0
[mc-image-helper] 13:49:03.573 INFO : Fabric launcher for minecraft 1.21.11 loader 0.18.4 is already available
[init] Copying any mods from /mods to /data/mods
[init] Copying any configs from /config to /data/config
[init] server.properties already created and managed manually
[mc-image-helper] 13:49:06.799 WARN : Attempting to synchronize input JAVA_WHITELIST file onto itself: /data/whitelist.json
[init] Setting initial memory to 1G and max to 16G
[init] Starting the Minecraft server...
Starting net.fabricmc.loader.impl.game.minecraft.BundlerClassPathCapture
[13:49:07] [main/INFO]: Loading Minecraft 1.21.11 with Fabric Loader 0.18.4
[13:49:07] [main/INFO]: Loading 58 mods:

[itzg]

https://docker-minecraft-server.readthedocs.io/en/latest/versions/minecraft/

[Mantaplatte]

Sorry im writing the first time in Github.

  test:
    image: itzg/minecraft-server:latest
    tty: true
    stdin_open: true
    environment:
      EULA: "TRUE"
      VERSION: "1.20.6"
      DIFFICULTY: "hard"
      ENABLE_WHITELIST: "TRUE"
      whitelist: |
        Mantaplatte
      OPS: |
        Mantaplatte
      OVERRIDE_SERVER_PROPERTIES: "false"
      MAX_MEMORY: "4G"
    labels:
      mc-router.host: "xxx"

  router:
    image: itzg/mc-router
    environment:
      TRACE: "TRUE"
      IN_DOCKER: true
      AUTO_SCALE_DOWN: true
      AUTO_SCALE_UP: true
      AUTO_SCALE_DOWN_AFTER: 0.5h
      AUTO_SCALE_ASLEEP_MOTD: "Server is asleep. Join again to wake it up!"
    ports:
      - "25565:25565"
      - "24454:24454"
    volumes:
      - /var/run/docker.sock:/var/run/docker.sock:ro

[itzg]

The Client also says the server is running in 1.21.10. Is there smth wrong with the mc-router?

No, mc-router has no influence on the version.

Are you sure you're not interpreting the message backwards? Maybe it means your client is the wrong version.

You're check the server logs right? What version does the Minecraft software say it's running?

You need to provide all of the container logs for me to provide any possible ideas.

[Mantaplatte]

Ok it has to be a problem with mc-router. When im trying to connect to a server behind mc-router the Client gives the "use 1.21.10".
If i try to connect to a server directly, it works fine.

Any idea whats wrong with mc-router? Did i miss smth?

[Mantaplatte]

[init] Running as uid=1000 gid=1000 with /data as 'drwxr-xr-x 7 1000 1000 4096 Feb  7 22:32 /data'
[init] Image info: buildtime=2026-02-04T12:57:41.493Z,version=java25,revision=6bb401f9ff2f98c1925944b546700fca4de73a93
[init] Resolving type given VANILLA
[init] Resolved version given 1.20.6 into 1.20.6
[init] Copying any configs from /config to /data/config
[init] server.properties already created and managed manually
[init] Setting initial memory to 1G and max to 4G
[init] Starting the Minecraft server...
Starting net.minecraft.server.Main
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 an unnamed module (file:/data/libraries/net/java/dev/jna/jna/5.14.0/jna-5.14.0.jar)
WARNING: Use --enable-native-access=ALL-UNNAMED to avoid a warning for callers in this module
WARNING: Restricted methods will be blocked in a future release unless native access is enabled

WARNING: A terminally deprecated method in sun.misc.Unsafe has been called
WARNING: sun.misc.Unsafe::objectFieldOffset has been called by com.google.common.util.concurrent.AbstractFuture$UnsafeAtomicHelper (file:/data/libraries/com/google/guava/guava/32.1.2-jre/guava-32.1.2-jre.jar)
WARNING: Please consider reporting this to the maintainers of class com.google.common.util.concurrent.AbstractFuture$UnsafeAtomicHelper
WARNING: sun.misc.Unsafe::objectFieldOffset will be removed in a future release
[22:49:06] [ServerMain/INFO]: Environment: Environment[sessionHost=https://sessionserver.mojang.com, servicesHost=https://api.minecraftservices.com, name=PROD]
[22:49:07] [ServerMain/INFO]: Loaded 1175 recipes
[22:49:07] [ServerMain/INFO]: Loaded 1276 advancements
[22:49:07] [Server thread/INFO]: Starting minecraft server version 1.20.6
[22:49:07] [Server thread/INFO]: Loading properties
[22:49:07] [Server thread/INFO]: Default game type: SURVIVAL
[22:49:07] [Server thread/INFO]: Generating keypair
[22:49:07] [Server thread/INFO]: Starting Minecraft server on *:25565
[22:49:07] [Server thread/INFO]: Using epoll channel type
[22:49:07] [Server thread/INFO]: Preparing level "world"
[22:49:09] [Server thread/INFO]: Preparing start region for dimension minecraft:overworld
[22:49:09] [Worker-Main-4/INFO]: Preparing spawn area: 0%
[22:49:09] [Worker-Main-4/INFO]: Preparing spawn area: 0%
[22:49:10] [Worker-Main-1/INFO]: Preparing spawn area: 18%
[22:49:10] [Worker-Main-3/INFO]: Preparing spawn area: 22%
[22:49:11] [Worker-Main-4/INFO]: Preparing spawn area: 55%
[22:49:11] [Worker-Main-5/INFO]: Preparing spawn area: 69%
[22:49:11] [Server thread/INFO]: Time elapsed: 2766 ms
[22:49:11] [Server thread/INFO]: Done (4.161s)! For help, type "help"
[22:49:11] [Server thread/INFO]: Starting remote control listener
[22:49:11] [Server thread/INFO]: Thread RCON Listener started
[22:49:11] [Server thread/INFO]: RCON running on 0.0.0.0:25575

Thats the full log for the "test" container.

  test:
    image: itzg/minecraft-server:latest
    tty: true
    stdin_open: true
    environment:
      EULA: "TRUE"
      VERSION: "1.20.6"
      DIFFICULTY: "hard"
      ENABLE_WHITELIST: "TRUE"
      whitelist: |
        Mantaplatte
      OPS: |
        Mantaplatte
      OVERRIDE_SERVER_PROPERTIES: "false"
      MAX_MEMORY: "4G"
    ports:
      - "27777:25565"

    volumes:
      - ./opt/MCServerData/test:/data

[Mantaplatte]

Are you sure you're not interpreting the message backwards? Maybe it means your client is the wrong version.

I dont think so...Client was in 1.21.11 and the server logs say its in 1.21.11 as well.

[itzg]

Works fine for me using:

services:
  test:
    image: itzg/minecraft-server:latest
    pull_policy: always
    tty: true
    stdin_open: true
    environment:
      EULA: "TRUE"
      VERSION: "1.20.6"
#      DIFFICULTY: "hard"
#      ENABLE_WHITELIST: "TRUE"
#      whitelist: |
#        Mantaplatte
#      OPS: |
#        Mantaplatte
#      OVERRIDE_SERVER_PROPERTIES: "false"
      MAX_MEMORY: "4G"
    labels:
      mc-router.host: "localhost"
  router:
    image: itzg/mc-router
    pull_policy: always
    environment:
      TRACE: "TRUE"
      IN_DOCKER: true
      AUTO_SCALE_DOWN: true
      AUTO_SCALE_UP: true
      AUTO_SCALE_DOWN_AFTER: 0.5h
      AUTO_SCALE_ASLEEP_MOTD: "Server is asleep. Join again to wake it up!"
    ports:
      - "25565:25565"
      - "24454:24454"
    volumes:
      - /var/run/docker.sock:/var/run/docker.sock:ro

Router logs

2026-02-07T23:25:28.468169603Z time="2026-02-07T23:25:28Z" level=trace msg="Trace logs enabled"
2026-02-07T23:25:28.468462651Z time="2026-02-07T23:25:28Z" level=debug msg="Using Docker API version negotiation"
2026-02-07T23:25:28.468472915Z time="2026-02-07T23:25:28Z" level=trace msg="Performing initial listing of Docker containers"
2026-02-07T23:25:28.678193404Z time="2026-02-07T23:25:28Z" level=info msg="Created route mapping" backend="172.20.0.2:25565" serverAddress=localhost
2026-02-07T23:25:28.678219695Z time="2026-02-07T23:25:28Z" level=debug msg="Beginning scale down" backendEndpoint="172.20.0.2:25565"
2026-02-07T23:25:28.678222994Z time="2026-02-07T23:25:28Z" level=info msg="Monitoring Docker for Minecraft containers"
2026-02-07T23:25:28.680705232Z time="2026-02-07T23:25:28Z" level=info msg="Listening for Minecraft client connections" listenAddress=":25565"
2026-02-07T23:25:43.469638189Z time="2026-02-07T23:25:43Z" level=trace msg="Listing Docker containers"
2026-02-07T23:25:54.823473634Z time="2026-02-07T23:25:54Z" level=debug msg="Got connection" client="172.20.0.1:40422"
2026-02-07T23:25:54.823510242Z time="2026-02-07T23:25:54Z" level=trace msg="Reading packet" client="172.20.0.1:40422"
2026-02-07T23:25:54.824603886Z time="2026-02-07T23:25:54Z" level=trace msg="Reading frame" client="172.20.0.1:40422"
2026-02-07T23:25:54.824636353Z time="2026-02-07T23:25:54Z" level=debug msg="Read frame length" client="172.20.0.1:40422" length=16
2026-02-07T23:25:54.824639273Z time="2026-02-07T23:25:54Z" level=debug msg="Reading frame content" client="172.20.0.1:40422" length=16 total=16
2026-02-07T23:25:54.824640791Z time="2026-02-07T23:25:54Z" level=debug msg="Read frame" client="172.20.0.1:40422" frame="Frame:[len=16, payload=0X00FE05096C6F63616C686F737463DD02]"
2026-02-07T23:25:54.824642277Z time="2026-02-07T23:25:54Z" level=debug msg="Read packet" client="172.20.0.1:40422" packet="Frame:[len=17, packetId=0, data=0XFE05096C6F63616C686F737463DD02]"
2026-02-07T23:25:54.824644805Z time="2026-02-07T23:25:54Z" level=debug msg="Got packet" client="172.20.0.1:40422" length=17 packetID=0
2026-02-07T23:25:54.824646051Z time="2026-02-07T23:25:54Z" level=debug msg="Got handshake" client="172.20.0.1:40422" handshake="&{766 localhost 25565 2}"
2026-02-07T23:25:54.824647711Z time="2026-02-07T23:25:54Z" level=trace msg="Reading packet" client="172.20.0.1:40422"
2026-02-07T23:25:54.824648917Z time="2026-02-07T23:25:54Z" level=trace msg="Reading frame" client="172.20.0.1:40422"
2026-02-07T23:25:54.824799981Z time="2026-02-07T23:25:54Z" level=debug msg="Read frame length" client="172.20.0.1:40422" length=22
2026-02-07T23:25:54.824807354Z time="2026-02-07T23:25:54Z" level=debug msg="Reading frame content" client="172.20.0.1:40422" length=22 total=22
2026-02-07T23:25:54.824808822Z time="2026-02-07T23:25:54Z" level=debug msg="Read frame" client="172.20.0.1:40422" frame="Frame:[len=22, payload=0X000469747A675CDDFD26FC864981B52EC42BB10BFDEF]"
2026-02-07T23:25:54.824810240Z time="2026-02-07T23:25:54Z" level=debug msg="Read packet" client="172.20.0.1:40422" packet="Frame:[len=23, packetId=0, data=0X0469747A675CDDFD26FC864981B52EC42BB10BFDEF]"
2026-02-07T23:25:54.824823080Z time="2026-02-07T23:25:54Z" level=debug msg="Got user info" client="172.20.0.1:40422" player=itzg/5cddfd26-fc86-4981-b52e-c42bb10bfdef
2026-02-07T23:25:54.824890071Z time="2026-02-07T23:25:54Z" level=debug msg="Finding backend for server address" serverAddress=localhost
2026-02-07T23:25:54.824897373Z time="2026-02-07T23:25:54Z" level=debug msg="checked if player is allowed to wake up the server" client="172.20.0.1:40422" player=itzg/5cddfd26-fc86-4981-b52e-c42bb10bfdef server=localhost serverAllowsPlayer=true
2026-02-07T23:25:54.824899141Z time="2026-02-07T23:25:54Z" level=debug msg="Canceling scale down" backendEndpoint="172.20.0.2:25565"
2026-02-07T23:25:54.824900176Z time="2026-02-07T23:25:54Z" level=info msg="Waking up backend server" serverAddress=localhost
2026-02-07T23:25:54.833147298Z time="2026-02-07T23:25:54Z" level=trace msg="Listing Docker containers"
2026-02-07T23:25:54.901388973Z time="2026-02-07T23:25:54Z" level=info msg="Woke up backend server" backendHostPort="172.20.0.2:25565" serverAddress=localhost
2026-02-07T23:25:54.901422114Z time="2026-02-07T23:25:54Z" level=info msg="Connecting to backend" backendHostPort="172.20.0.2:25565" client="172.20.0.1:40422" player=itzg/5cddfd26-fc86-4981-b52e-c42bb10bfdef server=localhost
2026-02-07T23:25:54.901488261Z time="2026-02-07T23:25:54Z" level=debug msg="Relayed handshake to backend" amount=40
2026-02-07T23:25:59.910788068Z time="2026-02-07T23:25:59Z" level=trace msg="Listing Docker containers"
2026-02-07T23:26:14.910786174Z time="2026-02-07T23:26:14Z" level=trace msg="Listing Docker containers"
2026-02-07T23:26:31.343340030Z time="2026-02-07T23:26:31Z" level=trace msg="Listing Docker containers"

Server logs. Note the Starting minecraft server version 1.20.6

2026-02-07T23:25:29.101942581Z [init] Running as uid=1000 gid=1000 with /data as 'drwxr-x--- 7 1000 1000 4096 Feb  7 23:21 /data'
2026-02-07T23:25:29.103392948Z [init] Image info: buildtime=2026-02-04T12:57:41.493Z,version=java25,revision=6bb401f9ff2f98c1925944b546700fca4de73a93
2026-02-07T23:25:29.109550703Z [init] Resolving type given VANILLA
2026-02-07T23:25:30.928161583Z [init] Resolved version given 1.20.6 into 1.20.6
2026-02-07T23:25:30.956175503Z [init] Copying any configs from /config to /data/config
2026-02-07T23:25:32.080330423Z [mc-image-helper] 23:25:32.079 INFO  : Created/updated 1 property in /data/server.properties
2026-02-07T23:25:32.130529131Z [init] Setting initial memory to 1G and max to 4G
2026-02-07T23:25:32.137638915Z [init] Starting the Minecraft server...
2026-02-07T23:25:32.263164008Z Starting net.minecraft.server.Main
2026-02-07T23:25:32.997703657Z WARNING: A restricted method in java.lang.System has been called
2026-02-07T23:25:32.997750952Z WARNING: java.lang.System::load has been called by com.sun.jna.Native in an unnamed module (file:/data/libraries/net/java/dev/jna/jna/5.14.0/jna-5.14.0.jar)
2026-02-07T23:25:32.997752759Z WARNING: Use --enable-native-access=ALL-UNNAMED to avoid a warning for callers in this module
2026-02-07T23:25:32.997753810Z WARNING: Restricted methods will be blocked in a future release unless native access is enabled
2026-02-07T23:25:32.997754760Z 
2026-02-07T23:25:33.954911596Z WARNING: A terminally deprecated method in sun.misc.Unsafe has been called
2026-02-07T23:25:33.954940505Z WARNING: sun.misc.Unsafe::objectFieldOffset has been called by com.google.common.util.concurrent.AbstractFuture$UnsafeAtomicHelper (file:/data/libraries/com/google/guava/guava/32.1.2-jre/guava-32.1.2-jre.jar)
2026-02-07T23:25:33.954942594Z WARNING: Please consider reporting this to the maintainers of class com.google.common.util.concurrent.AbstractFuture$UnsafeAtomicHelper
2026-02-07T23:25:33.954943644Z WARNING: sun.misc.Unsafe::objectFieldOffset will be removed in a future release
2026-02-07T23:25:35.477812881Z [23:25:35] [ServerMain/INFO]: Environment: Environment[sessionHost=https://sessionserver.mojang.com, servicesHost=https://api.minecraftservices.com, name=PROD]
2026-02-07T23:25:36.253548607Z [23:25:36] [ServerMain/INFO]: Loaded 1175 recipes
2026-02-07T23:25:36.358327737Z [23:25:36] [ServerMain/INFO]: Loaded 1276 advancements
2026-02-07T23:25:36.585260940Z [23:25:36] [Server thread/INFO]: Starting minecraft server version 1.20.6
2026-02-07T23:25:36.585554112Z [23:25:36] [Server thread/INFO]: Loading properties
2026-02-07T23:25:36.585798536Z [23:25:36] [Server thread/INFO]: Default game type: SURVIVAL
2026-02-07T23:25:36.585822700Z [23:25:36] [Server thread/INFO]: Generating keypair
2026-02-07T23:25:36.623607578Z [23:25:36] [Server thread/INFO]: Starting Minecraft server on *:25565
2026-02-07T23:25:36.699428402Z [23:25:36] [Server thread/INFO]: Using epoll channel type
2026-02-07T23:25:36.735534808Z [23:25:36] [Server thread/INFO]: Preparing level "world"
2026-02-07T23:25:37.511939354Z [23:25:37] [Server thread/INFO]: Preparing start region for dimension minecraft:overworld
2026-02-07T23:25:37.519925008Z [23:25:37] [Server thread/INFO]: Preparing spawn area: 2%
2026-02-07T23:25:38.014605282Z [23:25:38] [Worker-Main-14/INFO]: Preparing spawn area: 51%
2026-02-07T23:25:38.519132594Z [23:25:38] [Worker-Main-1/INFO]: Preparing spawn area: 63%
2026-02-07T23:25:38.705690904Z [23:25:38] [Server thread/INFO]: Time elapsed: 1193 ms
2026-02-07T23:25:38.705947482Z [23:25:38] [Server thread/INFO]: Done (1.971s)! For help, type "help"
2026-02-07T23:25:38.706073821Z [23:25:38] [Server thread/INFO]: Starting remote control listener
2026-02-07T23:25:38.707634351Z [23:25:38] [Server thread/INFO]: Thread RCON Listener started
2026-02-07T23:25:38.707691494Z [23:25:38] [Server thread/INFO]: RCON running on 0.0.0.0:25575
2026-02-07T23:25:55.292765277Z [23:25:55] [User Authenticator #1/INFO]: UUID of player itzg is 5cddfd26-fc86-4981-b52e-c42bb10bfdef
2026-02-07T23:25:55.804557732Z [23:25:55] [Server thread/INFO]: itzg[/172.20.0.3:55070] logged in with entity id 1 at (-61.5, 63.0, 39.5)
2026-02-07T23:25:55.815956568Z [23:25:55] [Server thread/INFO]: itzg joined the game

[itzg]

Make sure you've pulled and applied all the newest images using:

docker compose pull
docker compose up -d

[Mantaplatte]

Quiet embarrasing.

There was another server automaticly starting on the Port 25565.

Thanks for the Help: :D