Pre-release protocol

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This page documents the changes from the last stable Minecraft release (currently 1.6.2, protocol 74) to the current pre-release. Note that this page contains bleeding-edge information that may not be completely or correctly documented. He who wishes to commandeer the merging of this into Protocol when an update is made must be sure to respect any changes that may have occured to the respective packets there.

Protocol History

13w36a - Added sound category byte to 0x3E - Changed 0xC8 to a string:int map

13w37b -

1.6.3 - Terrain fixes to help moving to 1.7, no packet changes from 1.6.2

1.6.4 -

13w38a/b/c -

13w39a - UUIDs added to spawn named entity, game state 'gamemode' byte -> float

Protocol Version

13w39a - 80

13w38a/b/c - 79

1.6.4 - 78

1.6.3 - 77

13w37b - 76

13w36a - 75

New Packets

None

Changed Packets

Chat Message (0x03)

The message from the server to the client can currently handle

  • A normal string that doesn't begin with ", { or [
  • A JSON string
  • A JSON array
  • A JSON object

The JSON format works as follows (minus the //comments): 

   {
       // Plain text
       "text": "Hello world",
       //or
       // Translatable string
       "translate": "multiplayer.player.joined",
       "with": [
           //This can be replaced another json object allowing the parts
           //to be styled/translated seperately
           "thinkofdeath",
       ],
       //Items in the extra section will be appended to the message.
       //They can strings or json objects. If included the array must 
       //not be empty
       "extra": [
           "Testing",
           {"translate":"demo.day.2"}
       ],
       //Controls whether the text is bold or not. Default false
       "bold":true,
       //Controls whether the text is italic or not. Default false
       "italic":false,
       //Controls whether the text is underlined or not. Default false
       "underlined": false, 
       //Controls whether the text is striked out or not. Default false
       "strikethrough": false,
       //Controls whether the text is randomised constantly or not. Default false
       "obfuscated": false,
       //Controls the color of the text
       //Supported 'colors':
       // * black
       // * dark_blue
       // * dark_green
       // * dark_aqua
       // * dark_red
       // * dark_purple
       // * gold
       // * gray
       // * dark_gray
       // * blue
       // * green
       // * aqua
       // * red
       // * light_purple
       // * yellow
       // * white
       // * obfuscated
       // * bold
       // * strikethrough
       // * underline
       // * italic
       // * reset
       "color":"red",
       //Executes the action once the text is clicked
       "clickEvent":{
           //The action to execute
           //Supported actions:
           // * open_url
           // * open_file
           // * run_command
           // * suggest_command
           "action":"run_command",
           //The value to run the action with
           //open_url: Url to open
           //open_file: File to open
           //run_command: Command to execute
           //suggest_command: Text to place in the player's text box
           "value": "/time set day",
       },
       //Displays the action apon hovering over the text
       "hoverEvent": {
           //The action to execute
           //Supported actions
           // * show_text
           // * show_achievement
           // * show_item
           "action":"show_text",
           //The value to the action with
           //show_text: Text to display can be a JSON object
           //show_achievement: Name of the achievemnt to display e.g: "achievement.openInventory"
           //show_item: JSON version of the item, must be quoted. e.g: "{id:35,Damage:5,Count:2,tag:{display:{Name:Testing}}}"
           "value": "Hello",
       },
   }


Spawn Named Entity (0x14)

Server to Client

The only named entities (at the moment) are players (either real or NPC/Bot). This packet is sent by the server when a player comes into visible range, not when a player joins.

Servers can, however, safely spawn player entities for players not in visible range. The client appears to handle it correctly.

At one point, the Notchian client was not okay with receiving player entity packets, including 0x14, that refer to its own username or Entity ID; and would teleport to the absolute origin of the map and fall through the Void any time it received them. However, in more recent versions, it appears to handle them correctly, by spawning a new entity as directed (though future packets referring to the entity ID may be handled incorrectly).

Packet ID Field Name Field Type Example Notes
0x14 Entity ID int 94453 Player ID
Player UUID string
Player Name string Twdtwd Max length of 16
X int 784 Player X as a fixed-point number
Y int 2131 Player Y as fixed-point number
Z int -752 Player Z as fixed-point number
Yaw byte 0 Player rotation as a packed byte
Pitch byte 0 Player rotation as a packed byte
Current Item short 0 The item the player is currently holding. Note that this should be 0 for "no item", unlike -1 used in other packets. A negative value crashes clients.
Metadata Metadata The 1.3 client crashes on packets with no metadata, but the server can send any metadata key of 0, 1 or 8 and the client is fine.
Total Size: 24 bytes + length of strings + metadata (at least 1)


Named Sound Effect (0x3E)

Server to client

Used to play a sound effect on the client.

All known sound effect names can be seen here.

Packet ID Field Name Field Type Example Notes
0x3E Sound name string step.grass 250
Effect position X int 250 effect X multiplied by 8
Effect position Y int 250 effect Y multiplied by 8
Effect position Z int 250 effect Z multiplied by 8
Volume float 9 1 is 100%, can be more
Pitch byte 1 63 is 100%, can be more
Sound Category Unsigned byte 6 Possible values:

MASTER: 0

MUSIC: 1

RECORDS: 2

WEATHER: 3

BLOCKS: 4

MOBS: 5

ANIMALS: 6

PLAYERS: 7

Total Size: 21 bytes + length of string


Change Game State (0x46)

Server to Client

This packet appeared with protocol version 10. Currently, it appears when a bed can't be used as a spawn point and when the rain state changes. it could have additional uses in the future.

The class has an array of strings linked to reason codes 0, 1, 2, and 3 but only the codes for 1 and 2 are null.

Packet ID Field Name Field Type Example Notes
0x46 Reason byte 0
Value float 0 Depends on reason
Total Size: 3 bytes

Reason codes

Code Effect Notes
0 Invalid Bed "tile.bed.notValid"
1 Begin raining
2 End raining
3 Change game mode "gameMode.changed" 0 - Survival, 1 - Creative, 2 - Adventure
4 Enter credits
5 Demo messages 0 - Show welcome to demo screen, 101 - Tell movement controls, 102 - Tell jump control, 103 - Tell inventory control
6
7 Fade value The current darkness value. 1 = Dark, 0 = Bright
8 Fade time Time in ticks for the sky to fade


Increment Statistic (0xC8)

Server to Client

Packet ID Field Name Field Type Example Notes
0xC8 Count int 5 Number of entrys
Entry Statistic's name string
Entry Amount int 5 The amount to increase by
Total Size: 9 bytes


Client Statuses (0xCD)

Client to server

Sent when the client is ready to complete login and when the client is ready to respawn after death.

Packet ID Field Name Field Type Example Notes
0xCD Payload byte 0 Bit field. 0: Initial spawn, 1: Respawn after death, 2: Request statistics
Total Size: 2 bytes

Removed Packets

None

Plugin Channels

MC|RPack

Field Name Field Type Example Notes
Resource pack URL UTF8 string http://example.com/pack.zip
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