User:Lou Montana/Sandbox

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Future Multiplayer Scripting page

The basics

• In Multiplayer, players are connected to a server that distributes information among them.
• The server can be either a dedicated machine, or hosted by a player; in the latter it means the server can have a player unit.
• Players can join a game after it started: they are considered "JIP" and scripting should be adapted to them.

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In Singleplayer, the game acts as a player-hosted server (isServer returns true).

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Some Multiplayer commands will not work in Singleplayer, such as netId !

Locality

Definitions

• LOCAL is an attribute for the machine where the command/script/function is executed.
• REMOTE means non local. All players are remote units to a dedicated server, for example.
• commands arguments and effects can be either local or global:

Template:EffArg	a local argument means an argument that is processed on the machine where the command is executed
Template:EffArg	a global argument means any unit, even a remote one
Template:EffArg	a local effect means that the effect will only happen on the machine where the command is executed
Template:EffArg	a global effect means that all the computers will receive it

See Locality in Multiplayer for more information.

Different machines

Machine	Conditions
Dedicated Server	isDedicated
Player Server	hasInterface && isServer
Client	hasInterface && not isServer
JIP Client	hasInterface && didJIP
Headless Client	not hasInterface && not isDedicated

• If you want to know if the current machine is a server (Dedicated Server or Player Server), use isServer.
• If you want to know if the current machine has a player (Player Server included), use hasInterface.

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• a Headless Client can be JIP
• even if it is highly unlikely, a server can be JIP, too!

General information about locality

• a player's unit is always local to the player's machine.
  • a dedicated server doesn't have a player unit (isNull player // returns true)
  • to know if a certain unit is a player, use isPlayer
• an AI group with a player-leader will be local to the player's computer.
  • a subordinate player being in a player-lead group will remain local to its computer (see bulletpoint #1)
• a driven vehicle is always local to its driver (not the commander, not the gunner)
  • editor-placed objects and empty vehicles are local to the server
  • editor-placed triggers are created on every machine unless specified otherwise ("Server Only" Eden Editor option ticked)
  • units created with createUnit will be local to the computer that issued the command
  • objects and vehicles created with createVehicle will be local to the computer that issued the command

Locality changes

• if the player-leader dies, the AI is transferred where the new leader is local (server in case of AI, client in case of another player)
• joining AI units will change locality to the new leader's computer
• a driver gets in an empty vehicle, locality will change from server to player
• locality can also change in the event of a ||Team Switch]] or usage of selectPlayer

Code examples

Code	Argu-ments	Effect	Description
remoteUnit setDamage 1;	Template:EffArg	Template:EffArg	Any unit (local or remote) will die, and all the computers will know
localUnit addMagazine "30Rnd_556x45_STANAG";	Template:EffArg	Template:EffArg	Only a local unit can have its inventory edited with this command, but all the machines will be notified: if a player looks into the localUnit inventory, the added magazine will be there
remoteUnit setFace "Miller";	Template:EffArg	Template:EffArg	Any unit (local or remote) can get its face changed, but the new face will not be propagated through the network. Only the local machine's player will see the effect of the command ⓘ This command should ideally be executed on every machine, for example with: [remoteUnit, "Miller"] remoteExec ["setFace", 0, true]; See Remote Execution paragraph for more information.
localCamera cameraEffect ["Internal", "Back"];	Template:EffArg	Template:EffArg	Only a local camera can be entered, and of course only the local machine will see through this camera

PublicVariable commands

PublicVariable commands allow to send global variables to specified machines.

• Network reception is guaranteed
• Short variable names should be used for network performance
• These commands shouldn't be used intensely for the same reason

Command	Effect
publicVariable	Set/update a variable value from the local machine to all the other machines (including server)
publicVariableServer	Set/update a variable value from a client to the server
publicVariableClient	Set/update a variable value from the local machine (not necessarily the server) to a specific client ⚠ The information will be lost if the targeted client disconnects!

How it works

The server has the variable ABC_Score to send to everyone, it then uses publicVariable "ABC_Score" (do not forget the quotes!)
This sends the variable name and value to the clients.

• If the variable is not yet declared on their machine, it will declare it as well.
• If the variable already exists, the value is overridden by the server's value.
• If the variable changes again on the server, it has to be manually publicVariable'd once again!
• A JIP player will synchronise server's public variables before executing init.sqf. See Initialization Order for more information.
  • A JIP player will not synchronise publicVariableClient-received variables after he disconnects/reconnects. Only server-known public variables sent with publicVariable will be synchronised.

Remote Execution

Arma 2 introduced the (now obsolete) Multiplayer framework, used as follow:

waitUntil{ not isNil "BIS_MPF_InitDone"; };
[nil, nil, rHINT, "Message to everyone!"] call RE;

Arma 3 alpha introduced BIS_fnc_MP:

["Message to everyone, including JIP  players!", "hint", true, true] call BIS_fnc_MP;

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These two methods above are considered OBSOLETE since Arma 3 v1.50 introduced two engine commands: remoteExec and remoteExecCall.

Arma 3 (> v1.50):

["Message to everyone, including JIP players!", 0, true] remoteExec ["hint"];

See Arma 3 Remote Execution for more information.

onPlayerConnected/onPlayerDisconnected events

These commands will execute code when a player is connecting or disconnecting. This code will run for players connecting in the lobby and for JIP players!

• addMissionEventHandler["PlayerConnected"]
• addMissionEventHandler["PlayerDisconnected"]

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Before 1.57 use BIS_fnc_addStackedEventHandler for onPlayerConnected/onPlayerDisconnected.

Join In Progress

A JIP player will have many information synchronised by the game.

Information	Arma 2	Arma 3
date/time	Template:task/	Template:task/
date/time + setDate/skipTime	Template:task	Template:task/
weather (overcast, fog)	Template:task/	Template:task/
weather + setOvercast/setFog/setRain	Template:task	Template:task/
time passed since mission start (time command)	Template:task/	Template:task/
publicVariable-sent variables	Template:task/	Template:task/
setVariable-assigned variables (when alternative syntax's public parameter is set to true)	Template:task/	Template:task/
remoteExec- and remoteExecCall-executed code if JIP prerequisites are met	N/A	Template:task/

See Join In Progress for more information.

See also

• Headless Client
• Locality in Multiplayer
• Commands by effects and arguments locality
  • Server-only commands
• Initialization Order
• Arma 3 Remote Execution