Archipelago/docs/network protocol.md

Archipelago General Client

Archipelago Connection Handshake

These steps should be followed in order to establish a gameplay connection with an Archipelago session.

1. Client establishes WebSocket connection to Archipelago server.
2. Server accepts connection and responds with a RoomInfo packet.
3. Client may send a GetDataPackage packet.
4. Server sends a DataPackage packet in return. (If the client sent GetDataPackage.)
5. Client sends Connect packet in order to authenticate with the server.
6. Server validates the client's packet and responds with Connected or ConnectionRefused.
7. Server may send ReceivedItems to the client, in the case that the client is missing items that are queued up for it.
8. Server sends Print to all players to notify them of the new client connection.

In the case that the client does not authenticate properly and receives a ConnectionRefused then the server will maintain the connection and allow for follow-up Connect packet.

Synchronizing Items

When the client receives a ReceivedItems packet, if the index argument does not match the next index that the client expects then it is expected that the client will re-sync items with the server. This can be accomplished by sending the server a Sync packet and then a LocationChecks packet.

Even if the client detects a desync, it can still accept the items provided in this packet to prevent gameplay interruption.

When the client receives a ReceivedItems packet and the index arg is 0 (zero) then the client should accept the provided items list as its full inventory. (Abandon previous inventory.)

Archipelago Protocol Packets

Packets are sent between the multiworld server and client in order to sync information between them. Below is a directory of each packet.

Packets are simple JSON lists in which any number of ordered network commands can be sent, which are objects. Each command has a "cmd" key, indicating its purpose. All packet argument types documented here refer to JSON types, unless otherwise specified.

An object can contain the "class" key, which will tell the content data type, such as "Version" in the following example.

Example:

[{"cmd": "RoomInfo", "version": {"major": 0, "minor": 1, "build": 3, "class": "Version"}, "tags": ["WebHost"], ... }]

(Server -> Client)

These packets are are sent from the multiworld server to the client. They are not messages which the server accepts.

• RoomInfo
• ConnectionRefused
• Connected
• ReceivedItems
• LocationInfo
• RoomUpdate
• Print
• PrintJSON
• DataPackage
• Bounced

RoomInfo

Sent to clients when they connect to an Archipelago server.

Arguments

Name	Type	Notes
version	NetworkVersion	Object denoting the version of Archipelago which the server is running. See NetworkVersion for more details.
tags	list[str]	Denotes special features or capabilities that the sender is capable of. Example: WebHost
password	bool	Denoted whether a password is required to join this room.
forfeit_mode	str	auto, enabled, disabled, auto-enabled or goal.
remaining_mode	str	enabled, disabled, goal
hint_cost	int	The amount of points it costs to receive a hint from the server.
location_check_points	int	The amount of hint points you receive per item/location check completed.
players	list[NetworkPlayer]	Sent only if the client is properly authenticated (see Archipelago Connection Handshake). Information on the players currently connected to the server. See NetworkPlayer for more details.
datapackage_version	int	Data version of the [data package](#Data Package Contents) the server will send. Used to update the client's (optional) local cache.
datapackage_versions	dict[str, int]	Data versions of the individual games' data packages the server will send.
seed_name	str	uniquely identifying name of this generation

forfeit_mode

Dictates what is allowed when it comes to a player forfeiting their run. A forfeit is an action which distributes the rest of the items in a player's run to those other players awaiting them.

• auto: Distributes a player's items to other players when they complete their goal.
• enabled: Denotes that players may forfeit at any time in the game.
• auto-enabled: Both of the above options together.
• disabled: All forfeit modes disabled.
• goal: Allows for manual use of forfeit command once a player completes their goal. (Disabled until goal completion)

remaining_mode

Dictates what is allowed when it comes to a player querying the items remaining in their run.

• goal: Allows a player to query for items remaining in their run but only after they completed their own goal.
• enabled: Denotes that players may query for any items remaining in their run (even those belonging to other players).
• disabled: All remaining item query modes disabled.

ConnectionRefused

Sent to clients when the server refuses connection. This is sent during the initial connection handshake.

Arguments

Name	Type	Notes
errors	list[str]	Optional. When provided, should contain any one of: InvalidSlot, SlotAlreadyTaken, IncompatibleVersion, or InvalidPassword.

Connected

Sent to clients when the connection handshake is successfully completed.

Arguments

Name	Type	Notes
team	int	Your team number. See NetworkPlayer for more info on team number.
slot	int	Your slot number on your team. See NetworkPlayer for more info on the slot number.
players	list[NetworkPlayer]	List denoting other players in the multiworld, whether connected or not. See NetworkPlayer for info on the format.
missing_locations	list[int]	Contains ids of remaining locations that need to be checked. Useful for trackers, among other things.
checked_locations	list[int]	Contains ids of all locations that have been checked. Useful for trackers, among other things.
slot_data	dict	Contains a json object for slot related data, differs per game. Empty if not required.

ReceivedItems

Sent to clients when they receive an item.

Arguments

Name	Type	Notes
index	int	The next empty slot in the list of items for the receiving client.
items	list[NetworkItem]	The items which the client is receiving. See NetworkItem for more details.

LocationInfo

Sent to clients to acknowledge a received LocationScouts packet and responds with the item in the location(s) being scouted.

Arguments

Name	Type	Notes
locations	list[NetworkItem]	Contains list of item(s) in the location(s) scouted. See NetworkItem for more details.

RoomUpdate

Sent when there is a need to update information about the present game session. Generally useful for async games.

Arguments

The arguments for RoomUpdate are identical to RoomInfo barring two:

Name	Type	Notes
hint_points	int	New argument. The client's current hint points.
players	list[NetworkPlayer]	Changed argument. Always sends all players, whether connected or not.

All arguments for this packet are optional.

Print

Sent to clients purely to display a message to the player.

Arguments

Name	Type	Notes
text	str	Message to display to player.

PrintJSON

Sent to clients purely to display a message to the player. This packet differs from Print in that the data being sent with this packet allows for more configurable or specific messaging.

Arguments

Name	Type	Notes
data	list[JSONMessagePart]	See JSONMessagePart for more details on this type.
type	str	May be present to indicate the nature of this message. Known types are Hint and ItemSend.
receiving	int	Is present if type is Hint or ItemSend and marks the destination player's ID.
item	NetworkItem	Is present if type is Hint or ItemSend and marks the source player id, location id and item id.

DataPackage

Sent to clients to provide what is known as a 'data package' which contains information to enable a client to most easily communicate with the Archipelago server. Contents include things like location id to name mappings, among others; see Data Package Contents for more info.

Arguments

Name	Type	Notes
data	DataPackageObject	The data package as a JSON object. More details on its contents may be found at Data Package Contents

Bounced

Sent to clients after a client requested this message be sent to them, more info in the Bounce package.

Arguments

Name	Type	Notes
data	dict	The data in the Bounce package copied

(Client -> Server)

These packets are sent purely from client to server. They are not accepted by clients.

• Connect
• Sync
• LocationChecks
• LocationScouts
• StatusUpdate
• Say
• GetDataPackage
• Bounce

Connect

Sent by the client to initiate a connection to an Archipelago game session.

Arguments

Name	Type	Notes
password	str	If the game session requires a password, it should be passed here.
game	str	The name of the game the client is playing. Example: A Link to the Past
name	str	The player name for this client.
uuid	str	Unique identifier for player client.
version	NetworkVersion	An object representing the Archipelago version this client supports.
tags	list[str]	Denotes special features or capabilities that the sender is capable of.

Authentication

Many, if not all, other packets require a successfully authenticated client. This is described in more detail in Archipelago Connection Handshake.

Sync

Sent to server to request a ReceivedItems packet to synchronize items.

Arguments

No arguments necessary.

LocationChecks

Sent to server to inform it of locations that the client has checked. Used to inform the server of new checks that are made, as well as to sync state.

Arguments

Name	Type	Notes
locations	list[int]	The ids of the locations checked by the client. May contain any number of checks, even ones sent before; duplicates do not cause issues with the Archipelago server.

LocationScouts

Sent to the server to inform it of locations the client has seen, but not checked. Useful in cases in which the item may appear in the game world, such as 'ledge items' in A Link to the Past. The server will always respond with a LocationInfo packet with the items located in the scouted location.

Arguments

Name	Type	Notes
locations	list[int]	The ids of the locations seen by the client. May contain any number of locations, even ones sent before; duplicates do not cause issues with the Archipelago server.

StatusUpdate

Sent to the server to update on the sender's status. Examples include readiness or goal completion. (Example: defeated Ganon in A Link to the Past)

Arguments

Name	Type	Notes
status	int	One of Client States. Follow the link for more information.

Say

Basic chat command which sends text to the server to be distributed to other clients.

Arguments

Name	Type	Notes
text	str	Text to send to others.

GetDataPackage

Requests the data package from the server. Does not require client authentication.

Arguments

Name	Type	Notes
exclusions	list[str]	Optional. If specified, will not send back the specified data. Such as, ["Factorio"] -> Datapackage without Factorio data.

Bounce

Send this message to the server, tell it which clients should receive the message and the server will forward the message to all those targets to which any one requirement applies.

Arguments

Name	Type	Notes
games	list[str]	Optional. Game names that should receive this message
slots	list[int]	Optional. Player IDs that should receive this message
tags	list[str]	Optional. Client tags that should receive this message
data	dict	Any data you want to send

Appendix

NetworkPlayer

A list of objects. Each object denotes one player. Each object has four fields about the player, in this order: team, slot, alias, and name. team and slot are ints, alias and name are strs.

Each player belongs to a team and has a slot. Team numbers start at 0. Slot numbers are unique per team and start at 1. Slot number 0 refers to the Archipelago server; this may appear in instances where the server grants the player an item.

alias represents the player's name in current time. name is the original name used when the session was generated. This is typically distinct in games which require baking names into ROMs or for async games.

from typing import NamedTuple
class NetworkPlayer(NamedTuple):
    team: int
    slot: int
    alias: str
    name: str

Example:

[
    {"team": 0, "slot": 1, "alias": "Lord MeowsiePuss", "name": "Meow"}, 
    {"team": 0, "slot": 2, "alias": "Doggo", "name": "Bork"},
    {"team": 1, "slot": 1, "alias": "Angry Duck", "name": "Angry Quack"},
    {"team": 1, "slot": 2, "alias": "Mountain Duck", "name": "Honk"}
]

NetworkItem

Items that are sent over the net (in packets) use the following data structure and are sent as objects:

from typing import NamedTuple
class NetworkItem(NamedTuple):
    item: int
    location: int
    player: int

In JSON this may look like:

[
    {"item": 1, "location": 1, "player": 0},
    {"item": 2, "location": 2, "player": 0},
    {"item": 3, "location": 3, "player": 0}
]

JSONMessagePart

Message nodes sent along with PrintJSON packet to be reconstructed into a legible message. The nodes are intended to be read in the order they are listed in the packet.

from typing import TypedDict, Optional
class JSONMessagePart(TypedDict):
    type: Optional[str]
    color: Optional[str]
    text: Optional[str]

type is used to denote the intent of the message part. This can be used to indicate special information which may be rendered differently depending on client. How these types are displayed in Archipelago's ALttP client is not the end-all be-all. Other clients may choose to interpret and display these messages differently. Possible values for type include:

• player_id
• item_id
• location_id

color is used to denote a console color to display the message part with. This is limited to console colors due to backwards compatibility needs with games such as ALttP. Although background colors as well as foreground colors are listed, only one may be applied to a JSONMessagePart at a time.

Color options:

• bold
• underline
• black
• red
• green
• yellow
• blue
• magenta
• cyan
• white
• black_bg
• red_bg
• green_bg
• yellow_bg
• blue_bg
• purple_bg
• cyan_bg
• white_bg

text is the content of the message part to be displayed.

Client States

An enumeration containing the possible client states that may be used to inform the server in StatusUpdate.

import enum
class CLientStatus(enum.IntEnum):
    CLIENT_UNKNOWN = 0
    CLIENT_READY = 10
    CLIENT_PLAYING = 20
    CLIENT_GOAL = 30

NetworkVersion

An object representing software versioning. Used in the Connect packet to allow the client to inform the server of the Archipelago version it supports.

from typing import NamedTuple
class Version(NamedTuple):
    major: int
    minor: int
    build: int

Data Package Contents

A data package is a JSON object which may contain arbitrary metadata to enable a client to interact with the Archipelago server most easily. Currently, this package is used to send ID to name mappings so that clients need not maintain their own mappings.

We encourage clients to cache the data package they receive on disk, or otherwise not tied to a session. You will know when your cache is outdated if the RoomInfo packet or the datapackage itself denote a different version. A special case is datapackage version 0, where it is expected the package is custom and should not be cached.

Note:

• Any ID is unique to its type across AP: Item 56 only exists once and Location 56 only exists once.
• Any Name is unique to its type across its own Game only: Single Arrow can exist in two games.

Contents

Name	Type	Notes
games	dict[str, GameData]	Mapping of all Games and their respective data
version	int	Sum of all per-game version numbers, for clients that don't bother with per-game caching/updating.

GameData

GameData is a dict but contains these keys and values. It's broken out into another "type" for ease of documentation.

Name	Type	Notes
item_name_to_id	dict[str, int]	Mapping of all item names to their respective ID.
location_name_to_id	dict[str, int]	Mapping of all location names to their respective ID.
version	int	Version number of this game's data