Client-Server Communication

The client can't change server stuff directly, and the server can't read local input. A NetworkEvent is the bridge between them.

If you haven't read Client vs Server yet, do that first.

Setting Up

Drop a NetworkEvent into Hidden and name it.

Client to Server

Pack your data into a NetMessage, then send it:

-- ClientScript
local event = Hidden.DoorEvent
local msg = NetMessage:New()
msg:AddString("action", "open")
event:InvokeServer(msg)

On the server, listen with InvokedServer:

-- ServerScript
local event = Hidden.DoorEvent

event.InvokedServer:Connect(function(sender: Player, msg: NetMessage)
    local action = msg:GetString("action")
    print(sender.Name .. " wants to " .. action)
end)

Server to Client

Send data back to one player, or blast it to everyone:

-- ServerScript
event:InvokeClient(msg, player) -- one player
event:InvokeClients(msg)        -- everyone

On the client, listen with InvokedClient:

-- ClientScript
event.InvokedClient:Connect(function(msg: NetMessage)
    local damage = msg:GetNumber("damage")
    print("You took " .. damage .. " damage!")
end)

Always check the data on the server. The client can send anything, so don't trust it blindly.

Mini Project: Remote Door

1. Create a NetworkEvent named DoorEvent.
2. Create a Part named Door.

ClientScript (in a ClientScript):

local event = Hidden.DoorEvent

Input.KeyDown:Connect(function(keyCode, gameFocused)
    if keyCode == Enums.KeyCode.E then
        local msg = NetMessage:New()
        msg:AddString("action", "toggle")
        event:InvokeServer(msg)
    end
end)

ServerScript (in ScriptService):

local event = Hidden.DoorEvent
local door = Environment.Door

local isOpen = false

event.InvokedServer:Connect(function(sender: Player, msg: NetMessage)
    local action = msg:GetString("action")
    if action == "toggle" then
        isOpen = not isOpen
        local c = door.Color
        door.Color = Color.New(c.R, c.G, c.B, isOpen and 0.5 or 1)
        door.CanCollide = not isOpen
    end
end)

Walk up to the door and press E. It should open. Press it again and it closes.

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Next: Making a Tool to build an item.