Lou Montana/Sandbox – User

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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

• LOCAL is an attribute for the machine where the command/script/function is executed.
• REMOTE is an attribute for all the other machines. All clients are remote to a server, for example.
• A player's unit is always local to the player's machine. A dedicated server doesn't have a player unit.
• commands arguments and effects can be either local or global:
  • a local argument means an argument that is processed on the machine where the command is executed
  • a global argument means any unit, even a remote one
  • a local effect means that the effect will only happen on the machine where the command is executed
  • a global effect means that all the computers will receive it

See Locality in Multiplayer for more information.

Examples

Code	Arguments	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 addEventHandler ["FiredMan", { hint "remoteUnit fired"; }];	Template:EffArg	Template:EffArg	An event handler can be added to any unit (local or remote), but the code will only execute on the machine that ran the code
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 – no network traffic is generated here

Different machines

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

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 as 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.

See also

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