Pre-release protocol

Revision as of 11:35, 15 February 2012 by SirCmpwn (talk | contribs)
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This page documents the changes from the last stable Minecraft release (currently 1.1) to the current pre-release

New packets

Entity Head Look (0x23)

Changes the direction an entity's head is facing.

Packet ID Field Name Field Type Example Notes
0x23 Entity ID int
Head Yaw byte Head yaw in steps of 2π/256
Total Size: 6 bytes

Update Tile Entity (0x84)

Essentially a block update on a tile entity.

Packet ID Field Name Field Type Example Notes
0x84 X int
Y short
Z int
Action byte The type of update to perform
Custom 1 int Varies
Custom 2 int Varies
Custom 3 int Varies
Total Size: 24 bytes


  • 1: Set mob displayed inside a mob spawner. Custom 1 contains the mob type

Changed packets

Login Request (0x01)

World height was changed to an integer.

Packet ID Field Name Field Type Example Notes
0x01 Entity ID int 1298 The Players Entity ID
Not used string (empty string) Not used
Map Seed long 971768181197178410 The server's map seed. Must be sent in respawn packets by the client.
Level Type string DEFAULT DEFAULT or SUPERFLAT; level-type in
Server mode int 0 0 for survival, 1 for creative
Dimension byte 0 -1: The Nether, 0: The Overworld, 1: The End
Difficulty byte 1 0 thru 3 for Peaceful, Easy, Normal, Hard
World height int 256 Defaults to 256
Max players unsigned byte 8 Used by the client to draw the player list
Total Size: 28 bytes + length of strings

TODO: Figure out other packets

Handshake (0x02)

Client to Server

The hostname and port were added to this packet, most likely to allow virtual hosting .(sample implementation)

Packet ID Field Name Field Type Example Notes
0x02 UsernameAndHost string TkTech;localhost:25565 The username of the player attempting to connect, and the host he is connecting to, seperated by a semicolon.
Total Size: 3 bytes + length of strings

Mob Spawn (0x18)

New byte field: head yaw

This needs confirmation!

Packet ID Field Name Field Type Example Notes
0x18 EID int 446 Entity ID
Type byte 91 The type of mob. See Entities#Mobs
X int 13366 The Absolute Integer X Position of the object
Y int 2176 The Absolute Integer Y Position of the object
Z int 1680 The Absolute Integer Z Position of the object
Yaw byte -27 The yaw in steps of 2π/256
Pitch byte 0 The pitch in steps of 2π/256
Head Yaw byte Head yaw in steps of 2π/256
Metadata Metadata 127 Varies by mob, see Entities
Total Size: 21 bytes + Metadata (at least 1)

Other changes

Protocol version is now 27.

Protocol History


  • 12w07a
  • Protocol version is now 27
  • Updated packets: 0x01, 0x09, 0x33


  • 12w06a
  • Protocol version is now 25
  • New packet: 0x84


  • 12w04a
  • Protocol version has not been changed
  • Handshake Packet by client (0x02) now contains the server host and port
  • Window Open Packet (0x64): WindowTitle is now longer than accepted by older clients. Contains a keyword such as "container.furnace"


  • 12w03a
  • Protocol version is now 24
  • New packet: 0x23
  • MobSpawn: new field, 1 byte inserted before metadata.