Pre-release protocol
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
2012-05-03
- 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
