Quickstart

Flux has two entry points. Call Flux.Server(name) on the server and Flux.Client(name) on the client with the same name, and the two objects are connected.

The name is the channel identifier. It is written into every packet as a length-prefixed string, so both sides have to agree on it exactly. Matching is case-sensitive.

Server example

ServerScriptService/Example.server.luau

l-- server
local Flux = require(game.ReplicatedStorage.Flux)
local Ping = Flux.Server("Ping")

Ping:Connect(function(player, msg)
    print("got", msg, "from", player)
end)

Client example

StarterPlayerScripts/Example.client.luau

-- client
local Flux = require(game.ReplicatedStorage.Flux)

Flux.Client("Ping"):Fire("hello")

Reliable and unreliable delivery

Every Flux event carries both channels. There is no second object to create, so pick the method that matches the message.

-- Guaranteed delivery, ordered. Use for state changes.
Damage:Fire(player, 25)
Damage:FireAll(roundWinner)

-- May be dropped or reordered. Use for high-frequency, disposable data.
Position:FireUnreliable(player, character.PrimaryPart.CFrame)
Position:FireAllUnreliable(tick())

Unreliable packets are subject to Roblox’s UnreliableRemoteEvent size limit. Keep them to a single small payload, such as a CFrame or a couple of numbers, and never rely on them arriving.

Client-to-server invocations

An invocation is a round trip. The client sends a request, the server’s OnInvoke handler runs, and its return values come back to the caller.

local Shop = Flux.Server("Shop")

Shop.OnInvoke = function(player, itemId: string)
	local ok = grantItem(player, itemId)
	if not ok then
		error("Insufficient funds")
	end
	return true, itemId
end

local Shop = Flux.Client("Shop")

-- Invoke yields the calling thread until the server responds.
local ok, purchased = Shop:Invoke("sword")
print(ok, purchased) --> true sword

Client:Invoke errors if the server handler errors or if the request times out, so wrap it when failure is expected:

local success, result = pcall(function()
	return Shop:Invoke("legendary_sword")
end)

if not success then
	warn("Purchase failed:", result) --> "Insufficient funds"
end

Invocations only run from client to server. The server has no Invoke method and the client has no OnInvoke property. See Invocations for the pattern to use when you need data from a client.

Adding a schema

Passing a schema replaces the dynamic encoder with a fixed layout. It removes the per-value type tag from every argument and narrows numbers to the width you declare.

local Flux = require(ReplicatedStorage.Flux)
local T = Flux.Types

local Damage = Flux.Server("Damage", {
	T.Instance(),  -- the humanoid that was hit
	T.UInt16(),    -- damage amount, 0-65535
})

Damage:FireAll(humanoid, 250)

Declare the same schema on both sides, then read on for the full rules.

Schemas

Fixed layouts, composites, and when they pay off.

Generics

Get real autocomplete on Fire, Connect and Invoke.

Getting Started

Guides

Concepts

Reference

Server example

Client example

Reliable and unreliable delivery

Client-to-server invocations

Adding a schema

Schemas

Generics

​Server example

​Client example

​Reliable and unreliable delivery

​Client-to-server invocations

​Adding a schema

Schemas

Generics

Server example

Client example

Reliable and unreliable delivery

Client-to-server invocations

Adding a schema