Pre-release protocol

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This page documents the changes from the last stable Minecraft release (currently 1.2.5) to the current pre-release (or weekly release).

New packets

Tab-complete (0xCB)

Two-way

Sent C->S when the user presses [tab] while writing text. The payload contains all text behind the cursor.

The server responds with an auto-completion of the last word sent to it. In the case of regular chat, this is a player username. Command names and parameters are also supported.

In the event of more than one possible completion, the server responds with the options packed into the single string field, separated by a null character. Note that as strings are UTF-16, this is two bytes wide.

Packet ID Field Name Field Type Example Notes
0xCB Text string
Total Size: 3 bytes + length of string

Locale and View Distance (0xCC)

Client to server

Sent when the player connects, or when settings are changed.

Packet ID Field Name Field Type Example Notes
0xCC Locale string en_GB
View distance byte 0 0-3 for 'far', 'normal', 'short', 'tiny'.
Chat flags byte 8 Bit field. 0: chat enabled, 2: colors enabled
Unknown byte 0 First three bits(bitmask 0x7) are used as a number, bit four(bitmask 0x8) is used as bool
Total Size: 8 bytes + length of string

Encryption Key Response (0xFC)

Two-Way

See Protocol Encryption for information on this packet.

Packet ID Field Name Field Type Example Notes
0xFC Shared secret length short
Shared secret byte array
Total Size: 3 bytes + length of shared secret

Encryption Key Request (0xFD)

Server to client

See Protocol Encryption for information on this packet.

Packet ID Field Name Field Type Example Notes
0xFD Server id string
Public key length short
Public key byte array
Total Size: 5 bytes + length of string + length of key

Named Sound Effect (0x3E)

Server to client

Used to play a sound effect on the client.

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 with 8
Effect position Z int 250 effect Z multiplied with 8
Volume byte 9 63 is 100%, can be more
Pitch byte 63 63 is 100%, can be more
Total Size: 17 bytes + length of string

Changed packets

Login Request (0x01)

Two-Way

See Protocol Encryption for information on logging in.

Client to Server

Just 1 byte C->S

Packet ID
0x01

Server to Client

Packet ID Field Name Field Type Example Notes
0x01 Entity ID int 1298 The Players Entity ID
Level Type string default default or SUPERFLAT; level-type in server.properties
Server mode byte 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
Not used unsigned byte 0 Only 0 observed from vanilla server, was previously world height
Max players unsigned byte 8 Used by the client to draw the player list
Total Size: 12 bytes + length of strings

Handshake (0x02)

Client to server

See Protocol Encryption for information on logging in.

Packet ID Field Name Field Type Example Notes
0x02 Protocol Version byte 32
Username string TkTech The username of the player attempting to connect
Server Host string localhost
Server Port int 25565
Total Size: 10 bytes + length of strings

Respawn (0x09)

Two-Way

Sent by the client when the player presses the "Respawn" button after dying. The server then teleports the user to the spawn point, and sends a respawn packet in response. The client will not leave the respawn screen until it receives a respawn packet.

To change the player's dimension (overworld/nether/end), send them a respawn packet with the appropriate dimension, followed by prechunks/chunks for the new dimension, and finally a position and look packet. You do not need to unload chunks, the client will do it automatically.

Client to Server

Packet ID
0x09

Server to Client

Packet ID Field Name Field Type Example Notes
0x09 Dimension int 1 -1: The Nether, 0: The Overworld, 1: The End
Difficulty byte 1 0 thru 3 for Peaceful, Easy, Normal, Hard. 1 is always sent c->s
Creative mode byte 1 0 for survival, 1 for creative.
World height short 256 Defaults to 256
Level Type string default See 0x01 login
Total Size: 11 bytes + length of string

Protocol History

2012-05-10

  • 12w19a
  • No packet changes, but an other encryption algorythm is used, described in Protocol Encryption

2012-05-03

  • 12w18a
  • New packet: 0x3D Name Sound Effect
  • Changed packet: 0x01 Login Request
  • Changed packet: 0x02 Handshake
  • Changed packet: 0xCA Player Abilities
  • Changed packet: 0xCC Locale and View Distance
  • Changed packet: 0x09 Respawn
  • Removed packet: 0x32 Map Column Allocation
  • This items are not enchantable in this version: 0x103, 0x105, 0x15A, 0x167, 0x10C, 0x10D, 0x10E, 0x10F, 0x122, 0x110, 0x111, 0x112, 0x113, 0x123, 0x10B, 0x100, 0x101, 0x102, 0x124, 0x114, 0x115, 0x116, 0x117, 0x125, 0x11B, 0x11C, 0x11D, 0x11E, 0x126

2012-04-26

  • 12w17a
  • Protocol version is now 31
  • RC4 based encryption, described in Protocol Encryption
  • Changed packet: 0x01 Login Request
  • Changed packet: 0x02 Handshake
  • Changed packet: 0xCC Locale and View Distance
  • New packet: 0xFC Encryption Key Response
  • New packet: 0xFD Encryption Key Request
  • New Item: Book & Quills (0x182) is enchantable
  • New Item: Written Book (0x183) is enchantable

2012-04-19

  • 12w16a
  • Protocol version is now 30
  • New packet: 0xCB Tab-complete
  • New packet: 0xCC Locale and View Distance
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