Classic Protocol Extension/Proposals

Template

Add your proposal at the end of the page. Please use existing extensions as your guide to formatting. Please sign your proposals and comments by ending it with ~~~~.

===ExtensionName===
:Proposed by ~~~~
:Brief summary of the extension.
:'''Motivation''': Explain why this is needed or how it is useful.
:'''Client Behavior''': Detailed description of all new behavior that game clients need to implement in order to support this extension. Consider interaction with other extensions.
:'''Server Behavior''': Detailed description of all new behavior that game servers need to implement in order to support this extension. Consider interaction with other extensions.
:(Packet definitions, remarks, illustrations, and data tables go here)
:(Comments go here, please sign them)

Proposals

PlaySound

Proposed by !!!WARLOCK!!!

This extension allows server to play custom sound and musics on client.

Motivation: Servers can play custom musics or sound effects just in time or when something changes. Useful for gamemodes such as zombie survival, Servers can play zombie moaning sound while zombies are close to players. Player join and leave sounds, Kill streak sounds for games such as CTF, Radio and DJ class for players and sound effects for explosions and player deaths.

Client Behavior: Client must download and load, or load the sound directly from the URL with the ID. Client must be able to download any time after MapFinalize has sent. If the URL is empty then the Client must unload the sound with that ID. Client must unload the sound and load a new one if there's a sound with existing ID. Client must be able to play the sound right after receiving the PlaySound packet. The last playing sound can not be ignored or stopped when a new sound is going to be played. Files type must be in .WAV, otherwise they're ignored. Client must ignore downloading the existing files from Server if they're saved in drive. Client must not change the volume of all environments (Place/Destroy, Walk sounds) on SetVolume packet. Client must change a local variable for volume of next playing sound on SetVolume packet.

Server Behavior: Server must ignore sending the same url multiple times. Server can not send quick loops of sound due to network speed and client crash possibility. It's better to load all of required sounds after map load for better performance. Server must not send high sized file cause of time and speed it takes for download. Files type must be in .WAV, otherwise they're ignored. Server can change the volume before playing a sound. For a better networking, It's suggested to not send PlaySound instead of changing volume to zero.

LoadSound packet

Server to client

Packet ID	Field Name	Field Type	Example	Notes
0x?? (??)	ID	byte	143	Gives the URL an ID.
	URL	string	http://site.com/firstblood.wav	Address to a .WAV file, put this empty for unload.
	Total Size:	66 bytes

PlaySound packet

Server to client

Packet ID	Field Name	Field Type	Example	Notes
0x?? (??)	ID	byte	125	Plays the sound saved as ID.
	Total Size:	2 bytes

SetVolume packet

Server to client

Packet ID	Field Name	Field Type	Example	Notes
0x?? (??)	Percent	byte	87	Set the next playing sound(s) volume to a Percentage.
	Total Size:	2 bytes

ClientRedirection

Proposed by Sysr q (talk) 10:17, 12 May 2014 (UTC)

This extension allows servers to give clients a redirection to a separate, possibly "private" server.

Motivation: Allowing servers to redirect clients would be useful in several cases. Allowing a singular "hub" server to redirect players to various external (but related) servers depending on the gamemode they wish to play would allow tightly integrated networks. If servers are using an external "balancer" or some sort of Minecraft-aware proxy, the server could signal the proxy move its connection on the client's behalf to another server.

Client Behavior: Clients should be ready to receive a ClientRedirection packet any time after they receive a LevelFinalize packet. When clients receive a ClientRedirection packet, they should prompt the user with a message indicating the server they're being redirected too, and allow the user to continue or quit. Non-player clients (e.g., proxies) have the option of silently reconnecting on the client's behalf. Clients should then open a new connection to the newly redirected server, and begin standard negotiation protocol.

Server Behavior: Servers should only send a ClientRedirection packet after the they have sent a LevelFinalize packet. They should ensure the new server the client is being redirected to exists, and preferably is online and available.

ClientRedirection packet

Server to client

Packet ID	Field Name	Field Type	Example	Notes
0x?? (??)	Address	string	mc.example.org	Can be an IP address (IPv4/IPv6) or a hostname.
	Port	int	25565
	Name	string	Joe Blogg's Freebuild	(optional) User-friendly name to be displayed in user prompt.
Total Size:	133 bytes

BlockDefinitions

Proposed by Hetal, with contributions by fragmer.

This extension allows servers to define new block types with custom IDs and appearance.

Motivation: To allow defining block types without client modifications. To make full use of custom textures.

Client Behavior: This extension depends on EnvMapAppearance extension, and must only be enabled if BOTH extensions are mutually supported. Client should be able receive any number of DefineBlock and RemoveBlockDefinition packets during the level loading process (after receiving LevelInitialize and until receiving LevelFinalize packets). However, dependent on client, this can be sent after level loading (Some clients might just find it more extensible than others). Client must keep track of all defined blocks between level changes or until they are individually removed with RemoveBlockDefinition.

Client must be able to accept and render blocks as specified in DefineBlock packets. Clients must accept any valid definitions with BlockID between 128 and 255, inclusive. If a new definition is accepted for an already-defined BlockID, the old definition should be replaced. If RemoveBlockDefinition is received for a non-defined BlockID, it should be ignored.

Texturing: New textured are defined by altering terrain.png and specifying it with EnvSetMapAppearance packet. DefineBlock fields TopTextureID, SideTextureID, and BottomTextureID refer to a tile number within terrain.png. Tiles are numbered 0 (top-left corner) through 255 (bottom-right corner), increasing left-to-right within each row. Tiles 0-127 are reserved for standardized blocks. Refer to table 1 for a list of standard tiles (TODO). Block definitions can use these tiles, but texture makers should be careful not to accidentally overwrite tiles in this range (top half of terrain.png) to avoid changing appearance of standardized blocks that use them. Positions 128-255 (the bottom half of terrain.png) can be textured and used in any way.

Server Behavior: Server may send any number of DefineBlock packets when client expects it. Server should only use IDs of currently-defined blocks in block data sent in LevelDataChunk packets, SetBlock packets, or any other packets that expect block IDs.

Compatibility: TODO: Define what the server should do for non-supporting clients. Define how the client should store map files with block definitions. Maybe integrate this with ClassicWorld definition?

There are two packets, one for liquids and one for all other blocks. Both packets share a common number of fields initially, and are then followed by several packet specific fields.

DefineBlock Packet

Server to Client

Packet ID	Field Name	Field Type	Example	Notes
35	BlockID	byte	128	Between 128 and 255 (unsigned).
	Name	String	Cactus	Short, unique, player-friendly name for the block.
	Solidity	byte	1	Specified collision mode for this block type. Blocks may be walk-through (0), swim-through (1), or solid (2). Walk-through blocks do not collide with the player, and do not interfere with jumping. Players fall through these blocks. Swim-through blocks allow the player to descend or ascend slowly (at WalkSpeed), as if they were swimming. Solid blocks collide with the player. Players may walk on these.
	MovementSpeed	byte	1	Player movement speed modifier, defined relative to regular walk speed. Ratio to normal speed is computed with this formula: y = 2(x-128)/64 Thus a value of 0 translates to 0.25 ratio (25% speed), 128 to 1.00 ratio (100% speed), and 255 to 3.96 (396% speed). If Solidity is set to 0 or 1, speed is modified while player is inside (i.e. colliding with) the block. If Solidity is set to 2, speed is modified while player is standing on the block. If player is affected by several tiles, the lowest of all modifiers is used.
	TopTextureID	byte	1	Refers to a terrain.png tile. Between 0 and 255 (unsigned). Can be same as other texture IDs.
	SideTextureID	byte	2	Refers to a terrain.png tile. Between 0 and 255 (unsigned). Can be same as other texture IDs.
	BottomTextureID	byte	3	Refers to a terrain.png tile. Between 0 and 255 (unsigned). Can be same as other texture IDs.
	TransmitsLight	byte	0	Whether this block allows the sunlight to go through, for level-lighting purposes.
	WalkSound	byte	0	ID of a sound that client may play when player "steps" on, "walks" through, or "swims" through this tile. Must be one of sound IDs defined in https://github.com/andrewphorn/ClassiCube-Client/blob/master/src/main/java/com/mojang/minecraft/level/tile/Block.java#L24-L35. The sounds start from 0 (None).
	FullBright	byte	0	Whether or not the block/liquid is affected by shadows (such as lava). 0 = Affected (darkened when in shadow) 1 = Not affected (always bright).
	Shape	byte	0	Shape of the block model: Sprite = 0, Cube with height = 1-16 (e.g. slab would have a shape of '8', snow would have '2', dirt would have '16')
	BlockDraw	byte	0	Can be: 0 = fully opaque 1 = transparent (e.g. like glass) 2 = transparent but with no face culling of same neighbours (e.g. like leaves) 3 = translucent, where texture's alpha is blended (e.g. like ice or water) 4 = gas (e.g. like air)
	FogDensity	byte	0	Density of fog while client's camera is inside this block. Value of 0 means "do not change fog" -- level's default settings are used. Values between 1 and 255 are mapped to OpenGL's GL_FOG_DENSITY value for GL_EXP2 style fog with the following formula: GL_FOG_DENSITY = (x+1)/128 Thus value of 1 means density of ~0.0156, value of 127 means 1.0000, and 255 means 2.0000
	FogR	byte	255	Red component of the aforementioned fog. Only applies if FogDensity is above 0.
	FogG	byte	255	Green component of the aforementioned fog. Only applies if FogDensity is above 0.
	FogB	byte	255	Blue component of the aforementioned fog. Only applies if FogDensity is above 0.
Total Size:	80 bytes

RemoveBlockDefinition Packet

Server to Client

Packet ID	Field Name	Field Type	Example	Notes
36	BlockID	byte	128	Between 128 and 255
Total Size:	2 bytes

Future References: The client developers will be able to add more base blocks but then the server developers will have to change their Ids sent if the block is being occupied as a base block. If any of the fields are incorrectly configured, the client shall disconnect with an error message briefly describing why it crashed ("Invalid Custom Block located at Id : ID").

Example: Let's say I have a block called bullet being launched from a block (the block launching the bullet is not required for this situation). I could add that block's Id to the client using ADD_CUSTOM_BLOCK by AddCustomBlock((byte)128/*BulletBlockId*/, (byte)2);, and if my textureUrl in the EnvMapAppearance sent before/afterwards was actually containing a bullet in the correct slot, the block would inherit actual bullet textures making it realistic and yet again fun.

TABLE 1: TODO: list of tiles already defined in terrain.png, for both standard and CustomBlocks level 1 blocks.

TABLE 2: TODO: list of sounds available for footstep and breaking sounds

("Maybe allow this extension to have the ability to redefine blocks that are already defined in standard MC classic protocol and CPE? That would solve the problem defined in Future References and add more flexibility with the creation of custom blocks. This way, we would not have to agree on which blocks to define for each version of the CustomBlocks extension and instead create our own blocks to fit our specific purposes!" - Cheesse)

ColorCodeControl

Proposed by F (talk) 22:00, 28 August 2014 (UTC)

Gives servers an option to allow players to type in color codes, and a way to render & character in chat.

Motivation: Allow players to type in color codes and to use & in chat.

Client Behavior: When this extension is mutually supported, treat character sequence && as meaning "draw an & character", without modifying current color. Do not allow & to be typed or pasted into chat unless ColorCodeControl packet has been received with AllowColorCodes set to 1.

Server Behavior: When this extension is mutually supported, server may send ColorCodeControl packet to allow client to type or paste color codes. Server should treat && as described above.

ColorCodeControl packet

Server to Client

Packet ID	Field Name	Field Type	Example	Notes
??	AllowColorCodes	byte	0	0 = disallow 1 = allow
Total Size:	2 bytes

UnicodeChat

Proposed by F (talk) 22:48, 28 August 2014 (UTC)

Expands character encoding beyond ASCII. There are three ways to go about this:

1. Expand charset to 256 characters using Win-1252.
   • Pro: Easiest to implement in clients (few changes to FontRenderer needed) and servers (no multibyte character support needed).
   • Pro: No new packets needed.
   • Pro: Easy to create custom fonts.
   • Pro: Easy for servers to maintain compatibility with legacy clients, since only 128 characters need to be remapped, most of which have decent ASCII matches.
   • Pro: Low resource use (low RAM and VRAM use, no additional CPU use, small font file).
   • Con: Still only 256 characters. Only covers Latin-derived (English and Western/Central European) languages and common symbols.
2. Expand charset to Unicode Basic Multilingual Plane (BMP) with UCS-2 fixed-length encoding.
   • Pro: Lots of characters (~65k) covering most languages and symbols.
   • Pro: Not too hard to implement (characters still fixed-width, native support in WinAPI / Java / C#).
   • Pro: Free fonts available that covers all characters.
   • Con: New renderer (possibly third-party library) needed for rendering.
   • Con: Higher resource use (higher RAM and VRAM use, more CPU use, large font file).
   • Con: Very hard to create custom fonts.
   • Con: Still does not cover all characters.
   • Con: Hard for servers to maintain compatibility with legacy clients.
   • Con: Always uses 2 bytes per character for transmission (twice as much as ASCII/CP-1252).
3. Expand charset to Unicode Basic Multilingual Plane (BMP) with UTF-8 variable-length encoding.
   • Pro: Lots of characters (~65k) covering most languages and symbols.
   • Pro: Not too hard to implement (characters can be freely converted to/from UCS-2, which is natively support in WinAPI / C#).
   • Pro: Free fonts available that covers all characters.
   • Pro: Uses 1 byte per character for transmission, most of the time.
   • Con: New renderer (possibly third-party library) needed for rendering.
   • Con: Higher resource use (higher RAM and VRAM use, more CPU use, large font file).
   • Con: Hard to create custom fonts (unless some fallback rules are implemented).
   • Con: Still does not cover all characters.
   • Con: Hard for servers to maintain compatibility with legacy clients.
4. Expand charset to full Unicode with UTF-8 variable-length encoding. Includes all the supplemental Unicode planes.
   • Pro: Widely used in other software.
   • Pro: Theoretically covers all languages and symbols.
   • Pro: Uses 1 byte per character for transmission, most of the time.
   • Con: Does not actually cover all languages and symbols due to non-existence of 100% fonts.
   • Con: Hard to find free fonts that extend beyond the BMP.
   • Con: Harder to work with strings (due to variable-width characters).
   • Con: Third-party library needed for rendering.
   • Con: Highest resource use (highest RAM and VRAM use, most CPU use, largest font files).
   • Con: Hardest to implement (no native support in WinAPI / C#).
   • Con: Hard to create custom fonts (unless some fallback rules are implemented).
   • Con: Hard for servers to maintain compatibility with legacy clients.

ColorControl

Proposed by !!!WARLOCK!!!

Changes the color alpha (A) of Messagetypes to a custom number.

Motivation: Allows servers to make gradient/glass like text messages at Message Type's IDs.

Client Behavior: If this packet is received, Client should directly change the alpha color of the specified chat message into a custom number. If the default message ID `0` is received, client should be changing the alpha code of the all incoming and received chat lines into the specified number. The alpha code remains until the client disconnects from the server, and should be functional with all incoming and already received messages. Client should be able to receive this message after the Initial map load.

Server Behavior: Server can send this packet to clients right after client finished loading the initial map. Message type can be any of stated/defined numbers on the packet (Message Type).

ColorControl packet

Server to Client

Packet ID	Field Name	Field Type	Example	Notes
0x?? (??)	Message Type	byte	11	Message Type ID.
	Alpha Code	byte	154	Alpha code of color (From 0 - 255).
	Total Size:	3 bytes

SelectionCuboid v2

Proposed by FabTheZen, classic1234 and Rayne

Motivation: Allows the server to not only highlight parts of a world, but also determine whether those regions are walk through or not. This could be used to disallow players to walk inside restricted areas or zones which they are not allowed to build in. It could also be used as a jail when accompanied with the '-hax' option.

Client behavior: The client must receive the SelectionCuboid extension with version 2. It must also determine whether any selections on the map walk through or not.

Server behavior: The server behaves the same way SelectionCuboid v1 does.

MakeSelection packet v2

Server to Client

Packet ID	Field Name	Field Type	Example	Notes
0x?? (??)	SelectionID	byte	0	Numeric ID of the selection. Between 0 and 127.
	Label	string	SomeZone	Text label associated with the selection
	StartX	short	1	X coordinate of the starting point
	StartY	short	2	Y coordinate of the starting point
	StartZ	short	3	Z coordinate of the starting point
	EndX	short	5	X coordinate of the ending point
	EndY	short	6	Y coordinate of the ending point
	EndZ	short	7	Z coordinate of the ending point
	Red	short	255	Between 0 and 255.
	Green	short	34	Between 0 and 255.
	Blue	short	128	Between 0 and 255.
	Opacity	short	255	0 = fully transparent 255 = fully opaque
	Walkthrough	byte	0	0 = Not walkthrough 1 = Walkthrough
Total Size:	87 bytes

Player Animation

Proposed by ByteBit

Let the player to do certain actions/animations on the client

Motivation: Other players will be able to see the block another is holding or whether one placed a block or not. It makes the game's feel more realistic, because blocks don't pop out a no where.

Client Behavior: On recieve the client should perform the actions required for the animation.

Server Behavior: The server may send the packet if needed any time after the map is send.

AnimatePlayer packet

Server to Client

Packet ID	Field Name	Field Type	Example	Notes
0xAC (172)	Animation Type	byte	1	Specifies what animation to perform (0: Hold block; 1: Set block; 2: Destroy block; 3: Player name visibility)
	Player ID	byte	1	What player to perform this animation on
	Additional byte	byte	49 (Obsidian)	Needed for specific animations (Block type for 0,1 and 2; for 3: true(1)/false(0))
Total Size:	3 bytes

PlayerHealth

Proposed by Apotter96 (talk) 02:29, 26 July 2015 (UTC)alex96

Gives players life count that is controlled by the server and reflected by the client at the top left of the game screen. The server.

Motivation: RPG and Gun games can go more extensive if they wish with lives.

Client Behavior: Display player's lives at the top left of screen when the server sends the packet. On player connect, the server needs to tell the client the max amount of lives the player can have, in between 5 and 20. May also dictate how many lives the server is allowed to send. Both need to check with the other end so they can comply together.

Server Behavior: At any time the server can send the packet telling the client the amount of lives the player has. Once a player connects, the server needs to tell the client how many lives the player is allowed to have, in between 5 and 20. Both need to check with the other end so they can comply together.

UpdateLives packet

Server to client

Packet ID	Field Name	Field Type	Example	Notes
0x?? (??)	Lives	int	15	How many lives the player has
	MaxLives	int	15	The Max amount of lives
	Total Size:	2 bytes

UpdateLives packet

Client to server

Packet ID	Field Name	Field Type	Example	Notes
0x?? (??)	MaxLives	int	15	The Max amount of lives
	Total Size:	2 bytes

(Comments go here, please sign them)

EnvMapAppearance v2

Proposed by UnknownShadow200

This extension allows the server to specify custom texture packs, and tweak appearance of map edges.

Motivation: To provide more ways to customize map appearance, including functionality that's currently provided by World of Minecraft's scheme.

Client behavior: Client must be able to receive EnvSetMapAppearance v2 packets any time during level load (after the first LevelDataChunk packet is received and until the LevelFinalize packet is received). If the TexturePackURL field is blank or if the given file could not be loaded for any reason, then the texture pack should be reset to the client's default. If an unsupported block ID is given for SideBlock or EdgeBlock, it should be ignored. The given SideLevel value should be adjusted to fit between 0 and MapDepth, if necessary. Client should keep using these appearance parameters for future maps, unless specified otherwise by the server.

Server behavior: Server may send EnvSetMapAppearance v2 packets after the last LevelDataChunk packet is sent for a level. Server should not use any custom block IDs unless the client declared the appropriate CustomBlocks support level. To reset the texture pack to the client's default one, server should send an EnvSetMapAppearance v2 packet with empty string for TexturePackURL. To reset other fields, server should simply use the default values (listed below).

Block type restrictions: Only solid blocks are allowed to be used for SideBlock and EdgeBlock. Sprites (Sapling, Dandelion, Rose, BrownMushroom, RedMushroom, Rope, Fire) partial-height blocks (Slab, CobblestoneSlab, Snow), and transparent blocks (Air, Leaves, Glass) cannot be used for those fields.

EnvSetMapAppearance v2 packet

Server to Client

Packet ID	Field Name	Field Type	Example	Notes
0x1E (30)	TexturePackURL	string	http://example.com/mypack.zip	Texture pack's full URL. Must be a HTTP/HTTPS URL, in .zip format, and served with application/zip mime type.
	SideBlock	byte	7	Block ID. Default value is 7 (Admincrete).
	EdgeBlock	byte	8	Block ID. Default value is 8 (Water).
	SideLevel	short	31	Elevation from bottom of the map, in blocks. Value should be between 0 and MapDepth. Default value is MapDepth/2.
	CloudLevel	short	31	Elevation from bottom of the map, in blocks. Value should be between -32768 and 32767. Default value is MapDepth + 2.
	MaximumViewDistance	short	16	The maximum view distance the client is allowed to see, in blocks. Default is 0. (Client has no limit on view distance.)
Total Size:	73 bytes

Texture pack .zip format

Note: It is up to clients which files (except for terrain.png) they support in a texture pack. These clients are still considered to be compliant with the specification.

Note: Texture packs may also contain other files that are not listed below. If clients recognise these other files, then they may perform whatever is desired with them. Otherwise, clients must ignore these other files.

Note: If a texture pack does not contain a certain texture, clients should continue to use the existing texture from the previous texture pack.

Note: Servers are highly advised to avoid texture pack .zips over 4 MB, as these may be rejected by clients.

File name	Details
terrain.png	Texture atlas that contains the textures that are applied to blocks. Note: Clients must support this texture to be considered compliant with the specification.
animations.png	Texture atlas that contains the textures used for animations.
animations.txt	File that specifies how the textures in animations.png should be applied to the terrain.png texture atlas.
char.png	Default skin for humanoid models.
clouds.png	Texture applied to clouds rendered by the client.
The following may be utilised by clients if EnvWeatherType is mutually supported:
rain.png	Texture applied to rain rendered by the client.
snow.png	Texture applied to snow rendered by the client.
The following may be utilised by clients if ChangeModel is mutually supported: Note: The default texture for humanoid models is specified by char.png. Block models use textures from terrain.png.
x.png	Default texture applied to a model for model string x. For example, the Crocodile model has the model string croc. The default texture that would be applied is specified by croc.png.

animations.txt format

Each line is in the format: <TileX> <TileY> <FrameX> <FrameY> <Frame size> <Frames count> <Tick delay> - TileX and TileY indicate the coordinates of the tile in terrain.png that will be replaced by the animation frames. These range from 0 to 15. (inclusive of 15) - FrameX and FrameY indicates the pixel coordinates of the first animation frame in animations.png. The top left pixel coordinate is (0, 0) - Frame size indicates the size in pixels of an animation frame. - Frames count indicates the number of used frames. The first frame is located at (FrameX, FrameY), second frame at (FrameX + FrameSize, FrameY) and so forth. - Tick delay is the number of ticks a frame doesn't change. For instance, a value of 0 means that the frame would be changed every tick, while a value of 2 would mean 'replace with frame 1, don't change frame, don't change frame, replace with frame 2'.

ExtPlayerList v3

Proposed by Cheesse

This extension builds upon the current version and adds the ability to change the visibility of name tags.

Motivation: Provides more flexibility in naming of players and loading of skins, autocompletion, and player tab-list display. Separates tracking of in-game entities (spawned player models) and names on the player list. ExtAddPlayerName/ExtRemovePlayerName packets take over managing the player names list (tab-list), and ExtAddEntity3/DespawnPlayer packets are used only to manage in-game entities.Provides more flexibility in naming of players and loading of skins, autocompletion, and player tab-list display. Separates tracking of in-game entities (spawned player models) and names on the player list. ExtAddPlayerName/ExtRemovePlayerName packets take over managing the player names list (tab-list), and ExtAddEntity3/DespawnPlayer packets are used only to manage in-game entities.

Client Behavior: When ExtAddPlayerName packet is received for an unused NameID, a new name must be added to the player-name list. When receiving ExtAddPlayerName packet for an already-listed NameID, client must update its ListName, GroupName, and GroupRank. Names on the player-name list should be grouped by GroupName in the player-name list. Names within a GroupName should be sorted by GroupRank (in ascending order). Names with the same GroupName and GroupRank should be sorted alphabetically by ListName. Color codes may be either drawn or stripped from ListName, GroupName, and InGameName. Player-name list must persist when client changes worlds/maps.

When an ExtAddEntity3 packet is received, it must be treated as the SpawnPlayer packet. A player model must be spawned in-game at the given location, with InGameName text drawn above it. Skin should be loaded using the given SkinName for a player name. If SkinName appears to be a player name, skin should be downloaded from the default skin server. If SkinName appears to be a full URL to a PNG image (starts with http:// or https:// and ends with .png) then skin should be downloaded from that URL. If image is correctly sized/proportioned to use as a skin for the current model, it should be used. If a blank or unrecognized value is given for SkinName, or if given image could not be downloaded or used, then the default skin should be used. The client must also set the visibility according to NameVisibility and the collision ability of the entity according to CanCollide. When client receives ExtAddEntity3 packet for an already-spawned player, a duplicate entity must not be spawned and existing entity's position must not be changed. Instead their InGameName, SkinName, NameVisibility, and CanCollide attributes must be updated. If a negative EntityID is given for ExtAddEntity3, client must update player's own spawn point, InGameName, and SkinName. If any undefined value is given in the NameVisibility or CanCollide fields, the client should ignore these fields. The client must ignore regular SpawnPlayer packets, if any are received.

When a standard DespawnPlayer packet is received for a recognized EntityID, player model must be removed from a world. When ExtRemovePlayerName packet is received for a recognized NameID, their name must be removed from player-name list. Packets with out-of-range or unrecognized NameIDs must be ignored.

In-game entities must never be affected by ExtAddPlayerName or ExtRemovePlayerName packets. Player name list must never be affected by ExtAddEntity3 or DespawnPlayer packets.

Server Behavior: Unique NameID between 0 and 255 should be assigned to every online player or every player on a map for each map. When a new player connects to the server or joins a new map, ExtAddPlayerName must be sent. GroupName and GroupRank can be used in any way, for example to group players by map/world or rank/class/faction. Server must use ExtAddEntity3 in place of standard SpawnPlayer packet. Server should re-send ExtAddPlayerName packet, using the identical NameID, when player's ListName, GroupName, or GroupRank change. Server must reliably send an ExtRemovePlayerName packet when the player disconnects. Color codes are permitted in ListName, GroupName, and InGameName.

This extension only replaces the ExtAddEntity2 packet of the ExtPlayerList extension version 2. Thus, only the ExtAddEntity3 packet is shown here.

ExtAddEntity3 packet

Server to client

Packet ID	Field Name	Field Type	Example	Notes
0x?? (??)	EntityID	byte	5	Between 0 and 127
	InGameName	string	&cNotch	Player name to be shown in-game hovering above the player.
	SkinName	string	Notch	Name of the skin that should be used by the client. Could also be a URL to a PNG image.
	SpawnX	short	1	X coordinate (32 units per block) of entity's spawn location.
	SpawnY	short	2	Y coordinate (32 units per block) of entity's spawn location.
	SpawnZ	short	3	Z coordinate (32 units per block) of entity's spawn location.
	SpawnYaw	byte	4	Orientation (left-right) at the entity's spawn location.
	SpawnPitch	byte	5	Orientation (up-down) at the entity's spawn location.
	NameVisibility	byte	6	Visibility of the InGameName of the entity. Obstacles can be blocks or other entities. 0 = (Default) Visible only by hovering the cursor over the entity within view. Ignores any obstacles in the way. 1 = Visible only by hovering the cursor over the entity within view. Invisible when obstacles block the entity. 2 = Always visible within view (name tag shrinks over distance). Ignores any obstacles in the way. 3 = Always visible within view (name tag shrinks over distance). Invisible when obstacles block the entity. 4 = Always visible anywhere (name tag does not shrink over distance). Ignores any obstacles in the way. 5 = Always visible anywhere (name tag does not shrink over distance). Invisible when obstacles block the entity. 6 = Never visible.
	CanCollide	byte	0	0 = (default) Can collide with the player. 1 = Cannot collide with the player.
Total Size:	140 bytes

(Comments go here, please sign them)

HackControl v2

Proposed by Cheesse

This extension allows more control over the abilities of players.

Motivation: To gain control over the movement and action abilities of players.

Client Behavior: Client must be able to receive HackControl2 packets at any time and apply the changes defined in the packet immediately. Any value may be given in any field to allow or adjust an ability. If a negative value is given in any field, the client should set that value to its default. If 0 is given in any field, the client must deactivate that ability and prevent its use by the player unless otherwise stated.

Server Behavior: Server may send HackControl2 packets to successfully connected clients at any time.

HackControl2 packet

Server to client

Packet ID	Field Name	Field Type	Example	Notes
0x?? (??)	FlySpeed	byte	0	Defines the speed of flight in player units per quarter-second. A value of 0 or less means the player is not allowed to fly.
	NoClip	byte	0	0 = Prevent no-clipping 1 = Allow no-clipping
	WalkSpeed	byte	64	Defines the normal speed of walking in player units per quarter-second. Any negative value allows the player to travel at any speed and overrides any value set by RunSpeed.
	RunSpeed	byte	16	Helps define the ratio of the running speed to the walking speed. This value is then divided by 32 and added to 1 to get the ratio. A value less than or equal to 0 means the player is not allowed to run.
	AllowRespawn	byte	1	0 = Prevent respawning 1 = Allow respawning
	PointOfView	byte	0	0 = First-person view 1 = Third-person behind view 2 = Third-person front view Setting this field to a defined value will prevent the player from changing their point of view. Setting it to an undefined value will allow the player to switch points of view.
	JumpHeight	short	40	Maximum height in player units of the player's normal jump.
	SuperJumpHeight	short	9001	Maximum height in player units of any other jump abilities the player has, like using speed to get a higher jump. A SuperJumpHeight value of 0 means the player is not allowed to superjump. Any negative SuperJumpHeight will override any value in JumpHeight and allow the player to jump to any height.
Total Size:	11 bytes

(Comments go here, please sign them)

EnvWeatherType v2

Proposed by Cheesse

This extension allows the server to change the weather conditions and amount of fog.

Motivation: To allow the server to create a setting, scene or mood on a map; or to limit the players vision for things like smoke bombs in games. (Fog/View Distance is placed here because the EnvSetMapAppearance2 packet would be too big to include such a versatile feature.)

Client Behavior: Client must be able to receive EnvSetWeatherType2 packets at any time and apply the changes defined in the packet immediately. If an undefined value is used in the WeatherType or WeatherStrength fields, the client should ignore that value. If a negative value is given in the MaxFog field, the client should set that value to its own default. The client should make smooth changes between different strengths of weather and fog distances.

Server Behavior: Server may send EnvSetWeatherType2 packets to successfully connected clients at any time.

EnvSetWeatherType2 packet

Server to client

Packet ID	Field Name	Field Type	Example	Notes
0x?? (??)	WeatherType	byte	0	0 = Sunny 1 = Rainy 2 = Snowy
	WeatherStrength	byte	120	These values should be scaled such that a value of 120 should correspond to 100%. From 0-120.
	MaxFog	short	128	The distance in blocks of the wall of fog away from the player
Total Size:	5 bytes

(Comments go here, please sign them)

MessageTypes v2

Proposed by Cheesse

This extension adds new ways of presenting information to the player.

Motivation: To allow the server to send messages in different places and for limited times.

Client Behavior: Client must interpret the PlayerID field of the standard Message packet as the Message Type field. Certain values in this field correspond to different locations for messages on the screen. Any undefined values in this field should be ignored and presented as regular chat messages. Without mutual server-client support for this extension, this field should be ignored.

Server Behavior: Server may use the PlayerID field of the Message packet to have that message placed at a certain location on the player's screen.

MessageType Value	Meaning	Message Placement
0	Chat	In the chatbox.
1	Status1	At the top right of the screen.
2	Status2	At the top right of the screen below Status1.
3	Status3	At the top right of the screen below Status2.
11	BottomRight1	At the bottom right of the screen.
12	BottomRight2	At the bottom right of the screen above BottomRight1.
13	BottomRight3	At the bottom right of the screen above BottomRight2.
45	LeftHotbar	On top of the hotbar aligned to the left.
54	RightHotbar	On top of the hotbar aligned to the right.
100	BigAnnouncement	In large font slightly above the center of the screen.
200	SmallAnnouncement	Near the center of the screen below BigAnnouncement.

This extension does not define any new packets.

(Comments go here, please sign them)

ExtMapInfo

Proposed by Cheesse

This extension allows the server to send the client some of the map's metadata and other information

Motivation: To allow clients to save metadata with the maps they choose to save. This extension can also be modified to add more features to maps.

Client Behavior: Client must be able to receive FinalMapInfo packets at any time after a LevelInitialize packet has been received and before a FinalMapInfo packet has been received. Client should store the values in these fields in memory to be used later. The metadata defined in these fields come from those defined in the ClassicWorld file definitions. Client should ignore any LevelFinalize packets recieved.

Server Behavior: Server must send FinalMapInfo packets with the correct values after it has finished sending the client the raw block data after sending a LevelInitialize packet. The server should not send this packet at any other time. The server should never send any LevelFinalize packets to the client.

FinalMapInfo packet

Server to client

Packet ID	Field Name	Field Type	Example	Notes
0x?? (??)	"FormatVersion	byte	1	The FormatVersion is currently set to 1.
	"MapName"	string	main	The name of the map.
	"UUID"	byte array [16]	abcdefghijklmnop	The UUID of the map.
	"XSize"	short	128	The length of the map in the X dimension.
	"YSize"	short	128	The length of the map in the Y dimension.
	"ZSize"	short	128	The length of the map in the Z dimension.
	"CreatedBy"	string	Cheesse	The name of the author of the map. This should be an existing Classicube username.
	"MapGenSoftware"	string	Mapbuilder	The name of the software used to generate the map.
	"MapGenName"	string	Flat	The name of the generator function used to generate the map.
	"TimeCreated"	long	1234567890	The UTC Unix timestamp of the time the map was generated.
	"TimeLastModified"	long	1234567890	The UTC Unix timestamp of the time the map was last modified.
Total Size:	298 bytes

(Comments go here, please sign them)

BulkBlockUpdate

Proposed by Buzz, UnknownShadow200

Allows servers to send a single packet that contains 256 block updates.

Motivation: Reduce bandwidth usage and increase responsiveness to clients during times of heavy block updates, e.g. for large cuboids or lava survival servers.

Client Behavior: When this extension is mutually supported, treat the packet in the same manner as a list of up to 256 SetBlock packets.

Server Behavior: When this extension is mutually supported, server may send BlockBulkUpdate packet to the client after the LevelFinalize packet for the current level has been sent to the client.

BulkBlockUpdate packet

Server to Client

Packet ID	Field Name	Field Type	Example	Notes
0x25 (37)	Count	unsigned byte	0	The number of block updates used in this packet - 1. (e.g. a value of 0 means 1 block update is used).
	Indices	byte array[1024]	[52, 3443]	A packed list of the indices within the current level of the blocks that are to be updated. Each element is a 32 bit integer in big endian order.
	Blocks	byte array[256]	[5, 10]	A packed list of the new blocks to set at each corresponding index in the indices array.
Total Size:	1282 bytes