Pre-release protocol
This page documents the changes from the last stable Minecraft release (currently 1.12.1, protocol 338) to the current pre-release (currently 1.12.2-pre2, protocol 339). Note that this page contains bleeding-edge information that may not be completely or correctly documented.
One 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 occurred to the respective packets there.
Contents
Data types
No changes so far.
Packets
| ID | Packet name | Documentation | |
|---|---|---|---|
| Handshaking serverbound | |||
| 0x00 | Handshake | Current | Pre |
| Play clientbound | |||
| 0x1F | Keep Alive (clientbound) | Current | Pre |
| Play serverbound | |||
| 0x0B | Keep Alive (serverbound) | Current | Pre |
New/modified data types
No changes so far.
Block Actions
No changes so far.
Play
Clientbound
Keep Alive (clientbound)
 |
The following information needs to be added to this page: |
| "random ID" and such seem to no longer actually be the case. For the client, this doesn't matter (just parrot back the same data), but what the numbers actually mean and how the server uses them seem to be different now. |
The server will frequently send out a keep-alive, each containing a random ID. The client must respond with the same packet. If the client does not respond to them for over 30 seconds, the server kicks the client. Vice versa, if the server does not send any keep-alives for 20 seconds, the client will disconnect and yields a "Timed out" exception.
| Packet ID | State | Bound To | Field Name | Field Type | Notes |
|---|---|---|---|---|---|
| 0x1F | Play | Client | Keep Alive ID |
Serverbound
Keep Alive (serverbound)
The server will frequently send out a keep-alive, each containing a random ID. The client must respond with the same packet.
| Packet ID | State | Bound To | Field Name | Field Type | Notes |
|---|---|---|---|---|---|
| 0x0B | Play | Server | Keep Alive ID |
Handshaking
Clientbound
No changes so far.
Serverbound
Handshake
This causes the server to switch into the target state.
| Packet ID | State | Bound To | Field Name | Field Type | Notes |
|---|---|---|---|---|---|
| 0x00 | Handshaking | Server | Protocol Version | VarInt | See protocol version numbers (currently |
| Server Address | String | Hostname or IP, e.g. localhost or 127.0.0.1, that was used to connect. The Notchian server does not use this information. | |||
| Server Port | Unsigned Short | Default is 25565. The Notchian server does not use this information. | |||
| Next State | VarInt Enum | 1 for status, 2 for login |
Status
Clientbound
No changes so far.
Serverbound
No changes so far.
Login
Clientbound
No changes so far.
Serverbound
No changes so far.
