Packet Logger

A deep packet logging mod for Minecraft Fabric that captures all network traffic (´S2C´ and ´C2S´) with full NBT/Component data.

Use Cases

• Mod Development: Debug network communication between client and server
• Container Inspection: View exact contents of inventories with full NBT/Component data and copying them
• Reverse Engineering: Analyze server-side mechanics and packet structures
• Anti-Cheat Analysis: Understand what data the server sends and receives
• Learning: Understand how Minecraft's network protocol works

Usage

Keybind

Press F6 to open the config screen.

Packet Selection

Use the dual-list selector to choose which packets to log:

• S2C (Server → Client): Incoming packets like inventory updates, entity spawns, etc.
• C2S (Client → Server): Outgoing packets like clicks, movements, etc.

Log Modes

• Chat: Display packets in the game chat (truncated for readability)
• File: Save packets to log files with full data

Log Files

Logs are saved to:

MINECRAFT_FOLDER/config/packet-logger/packets_2026-01-04_15-30-45_servername.log

A new log file is created when:

• Joining a world/server
• Re-enabling logging after it was disabled

Example Output

[12:34:56.789] [S2C] InventoryS2CPacket {syncId:2,revision:1,id:"minecraft:generic_9x3",components:{"minecraft:container":[{item:{id:"minecraft:diamond_sword",count:1,components:{"minecraft:enchantments":{levels:{"minecraft:sharpness":5}}}},slot:0}]}}

Configuration

Config saved at: .minecraft/config/packet-logger-config.json

{
  "logPackets": true,
  "logMode": "FILE",
  "deepLogging": true,
  "selectedS2CPackets": ["InventoryS2CPacket"],
  "selectedC2SPackets": ["ClickSlotC2SPacket"]
}

Installation

Requirements

• Minecraft 1.21 - 1.21.11
• Fabric Loader 0.16.0+
• Fabric API

Download

You can download the mod from Modrinth. Simply place the downloaded .jar file into your .minecraft/mods folder.

Download on Modrinth

For Developers

Building

./gradlew build

Output: build/libs/packet-logger-1.0.0.jar

Project Structure

src/client/java/dev/redstone/packetlogger/
├── PackageLoggerClient.java       # Client entrypoint
├── config/
│   └── ModConfig.java             # Configuration
├── logger/
│   ├── PacketLogger.java          # Main logger
│   └── unpacker/                  # Specialized packet unpackers
│       ├── ItemStackFormatter.java
│       ├── InventoryS2CUnpacker.java
│       └── ...
├── mixin/client/
│   ├── ClientConnectionMixin.java # Packet interception
│   └── ...
└── screen/
    └── SimpleConfigScreen.java    # Config UI

Available Packets

S2C Packets (Server → Client)

Click to expand (108 packets)

• AdvancementUpdateS2CPacket
• BlockBreakingProgressS2CPacket
• BlockEntityUpdateS2CPacket
• BlockEventS2CPacket
• BlockUpdateS2CPacket
• BossBarS2CPacket
• BundleS2CPacket
• ChangeUnlockedRecipesS2CPacket
• ChatMessageS2CPacket
• ChatSuggestionsS2CPacket
• ChunkBiomeDataS2CPacket
• ChunkDataS2CPacket
• ChunkDeltaUpdateS2CPacket
• ChunkLoadDistanceS2CPacket
• ChunkRenderDistanceCenterS2CPacket
• ChunkSentS2CPacket
• ClearTitleS2CPacket
• CloseScreenS2CPacket
• CommandSuggestionsS2CPacket
• CommandTreeS2CPacket
• CooldownUpdateS2CPacket
• CraftFailedResponseS2CPacket
• DamageTiltS2CPacket
• DeathMessageS2CPacket
• DebugSampleS2CPacket
• DifficultyS2CPacket
• EndCombatS2CPacket
• EnterCombatS2CPacket
• EnterReconfigurationS2CPacket
• EntitiesDestroyS2CPacket
• EntityAnimationS2CPacket
• EntityAttachS2CPacket
• EntityAttributesS2CPacket
• EntityDamageS2CPacket
• EntityEquipmentUpdateS2CPacket
• EntityPassengersSetS2CPacket
• EntityPositionS2CPacket
• EntityS2CPacket
• EntitySetHeadYawS2CPacket
• EntitySpawnS2CPacket
• EntityStatusEffectS2CPacket
• EntityStatusS2CPacket
• EntityTrackerUpdateS2CPacket
• EntityVelocityUpdateS2CPacket
• ExperienceBarUpdateS2CPacket
• ExperienceOrbSpawnS2CPacket
• ExplosionS2CPacket
• GameJoinS2CPacket
• GameMessageS2CPacket
• GameStateChangeS2CPacket
• HealthUpdateS2CPacket
• InventoryS2CPacket
• ItemPickupAnimationS2CPacket
• LightUpdateS2CPacket
• LookAtS2CPacket
• MapUpdateS2CPacket
• NbtQueryResponseS2CPacket
• OpenHorseScreenS2CPacket
• OpenScreenS2CPacket
• OpenWrittenBookS2CPacket
• OverlayMessageS2CPacket
• ParticleS2CPacket
• PlayerAbilitiesS2CPacket
• PlayerActionResponseS2CPacket
• PlayerListHeaderS2CPacket
• PlayerListS2CPacket
• PlayerPositionLookS2CPacket
• PlayerRemoveS2CPacket
• PlayerRespawnS2CPacket
• PlayerSpawnPositionS2CPacket
• PlaySoundFromEntityS2CPacket
• PlaySoundS2CPacket
• ProfilelessChatMessageS2CPacket
• ProjectilePowerS2CPacket
• RemoveEntityStatusEffectS2CPacket
• RemoveMessageS2CPacket
• ScoreboardDisplayS2CPacket
• ScoreboardObjectiveUpdateS2CPacket
• ScoreboardScoreResetS2CPacket
• ScoreboardScoreUpdateS2CPacket
• ScreenHandlerPropertyUpdateS2CPacket
• ScreenHandlerSlotUpdateS2CPacket
• SelectAdvancementTabS2CPacket
• ServerMetadataS2CPacket
• SetCameraEntityS2CPacket
• SetTradeOffersS2CPacket
• SignEditorOpenS2CPacket
• SimulationDistanceS2CPacket
• StartChunkSendS2CPacket
• StatisticsS2CPacket
• StopSoundS2CPacket
• SubtitleS2CPacket
• SynchronizeRecipesS2CPacket
• TeamS2CPacket
• TickStepS2CPacket
• TitleFadeS2CPacket
• TitleS2CPacket
• UnloadChunkS2CPacket
• UpdateSelectedSlotS2CPacket
• UpdateTickRateS2CPacket
• VehicleMoveS2CPacket
• WorldBorderCenterChangedS2CPacket
• WorldBorderInitializeS2CPacket
• WorldBorderInterpolateSizeS2CPacket
• WorldBorderSizeChangedS2CPacket
• WorldBorderWarningBlocksChangedS2CPacket
• WorldBorderWarningTimeChangedS2CPacket
• WorldEventS2CPacket
• WorldTimeUpdateS2CPacket

C2S Packets (Client → Server)

Click to expand (47 packets)

• AcknowledgeChunksC2SPacket
• AcknowledgeReconfigurationC2SPacket
• AdvancementTabC2SPacket
• BoatPaddleStateC2SPacket
• BookUpdateC2SPacket
• ButtonClickC2SPacket
• ChatCommandSignedC2SPacket
• ChatMessageC2SPacket
• ClickSlotC2SPacket
• ClientCommandC2SPacket
• ClientStatusC2SPacket
• CloseHandledScreenC2SPacket
• CommandExecutionC2SPacket
• CraftRequestC2SPacket
• CreativeInventoryActionC2SPacket
• DebugSampleSubscriptionC2SPacket
• HandSwingC2SPacket
• JigsawGeneratingC2SPacket
• MessageAcknowledgmentC2SPacket
• PickFromInventoryC2SPacket
• PlayerActionC2SPacket
• PlayerInputC2SPacket
• PlayerInteractBlockC2SPacket
• PlayerInteractEntityC2SPacket
• PlayerInteractItemC2SPacket
• PlayerMoveC2SPacket
• PlayerSessionC2SPacket
• QueryBlockNbtC2SPacket
• QueryEntityNbtC2SPacket
• RecipeBookDataC2SPacket
• RecipeCategoryOptionsC2SPacket
• RenameItemC2SPacket
• RequestCommandCompletionsC2SPacket
• SelectMerchantTradeC2SPacket
• SlotChangedStateC2SPacket
• SpectatorTeleportC2SPacket
• TeleportConfirmC2SPacket
• UpdateBeaconC2SPacket
• UpdateCommandBlockC2SPacket
• UpdateCommandBlockMinecartC2SPacket
• UpdateDifficultyC2SPacket
• UpdateDifficultyLockC2SPacket
• UpdateJigsawC2SPacket
• UpdatePlayerAbilitiesC2SPacket
• UpdateSelectedSlotC2SPacket
• UpdateSignC2SPacket
• UpdateStructureBlockC2SPacket
• VehicleMoveC2SPacket

License

MIT

Credits

• Fabric API Team
• Minecraft Modding Community