Remote events and callbacks

Roblox games are multiplayer by default, so all games inherently communicate between the server and the players' connected clients. In the simplest case, as players move their characters, certain Humanoid properties, such as states, are communicated to the server, which passes this information to other connected clients.

Remote events and callbacks let you communicate across the client-server boundary:

• RemoteEvents enable one-way communication (sending a request and not yielding for a response).
• UnreliableRemoteEvents enable one-way communication for data that changes continuously or isn't critical to the game's state. These events trade ordering and reliability for improved network performance.
• RemoteFunctions enable two-way communication (sending a request and yielding until a response is received from the recipient).

Unlike bindable events, which have more limited utility, the use cases for remote events and functions are too numerous to list:

• Gameplay - Basic gameplay, such as a player reaching the end of a level, can require a remote event. A client script notifies the server, and server scripts reset the player's position.
• Server verification - If a player tries to drink a potion, do they actually have that potion? To ensure fairness, the server has to be the source of truth for a game. A client script can use a remote event to notify the server that the player is drinking a potion, and then server scripts can decide whether the player actually has that potion and whether to confer any benefits.
• User interface updates - As the game's state changes, server scripts can use remote events to notify clients of changes to scores, objectives, etc.
• In-game Marketplace purchases - For an example implementation that uses remote functions, see Prompt subscription purchases.

Quick reference#

The following tables serve as a quick reference for how to use RemoteEvents and RemoteFunctions to communicate between the client and server.

Remote events#

A RemoteEvent object facilitates asynchronous, one-way communication across the client-server boundary without yielding for a response.

To create a new RemoteEvent via the Explorer window in Studio:

1. Hover over the container into which you want to insert the RemoteEvent. In order to ensure both server and client access, it must be in a place where both sides can see it, such as ReplicatedStorage, although in some cases it's appropriate to store it in Workspace or inside a Tool.
2. Click the ⊕ button that appears to the right of the container's name and insert a RemoteEvent instance.
3. Rename the instance to describe its purpose.

Once you've created a RemoteEvent, it can facilitate one-way communication from client to server, from server to client, or from the server to all clients.

Client → server#

You can use a LocalScript to trigger an event on the server by calling the FireServer() method on a RemoteEvent. If you pass arguments to FireServer(), they pass to the event handler on the server with certain limitations. Note that the first parameter of the event handler on the server is always the Player object of the client that calls it, and additional parameters follow.

Client	RemoteEvent:FireServer(args)
Server	RemoteEvent.OnServerEvent:Connect(function(player, args))

local ReplicatedStorage = game:GetService("ReplicatedStorage")
local Workspace = game:GetService("Workspace")

-- Get reference to remote event instance
local remoteEvent = ReplicatedStorage:FindFirstChildOfClass("RemoteEvent")

local function onCreatePart(player, partColor, partPosition)
	print(player.Name .. " fired the RemoteEvent")
	local newPart = Instance.new("Part")
	newPart.Color = partColor
	newPart.Position = partPosition
	newPart.Parent = Workspace
end

-- Connect function to event
remoteEvent.OnServerEvent:Connect(onCreatePart)

local ReplicatedStorage = game:GetService("ReplicatedStorage")

-- Get reference to remote event instance
local remoteEvent = ReplicatedStorage:FindFirstChildOfClass("RemoteEvent")

-- Fire the remote event and pass additional arguments
remoteEvent:FireServer(Color3.fromRGB(255, 0, 0), Vector3.new(0, 25, -20))