Can RemoteEvents be two way? - roblox

Question

For example, would these scripts work, hang, or possibly give an error?
(In a script)
RemoteEvent = game:GetService("ReplicatedStorage"):WaitForChild("RemoteEvent")
RemoteEvent:FireClient()
RemoteEvent.onServerEvent:Wait()
print("Hello World")
(In a LocalScript)
RemoteEvent = game:GetService("ReplicatedStorage"):WaitForChild("RemoteEvent")
RemoteEvent.onClientEvent:Wait()
RemoteEvent:FireServer()

Answer 1

To simply answer your question, RemoteEvents do work both ways. The same event can be used from client-to-server as server-to-client.
Your example, as-is, will likely have some timing issues.
The server will start, fire on all zero clients, then wait for a client to send the signal back.
At some time later, a client will join and then wait for the server signal (which has already happened) and get stuck.
Depending on your desired logic, you could wait to execute the code when a player joins the game :
-- server Script
local PlayerService = game:GetService("Players")
local ReplicatedStorage = game:GetService("ReplicatedStorage")
local RemoteEvent = ReplicatedStorage.RemoteEvent
PlayerService.PlayerAdded:Connect( function(player)
-- Wait() will fire for any player that sends up the signal, so make sure that we know which player sent it
-- instead, connect to the signal to make sure we're listening to the right player
RemoteEvent.OnServerEvent:Connect( function(clientPlayer)
if clientPlayer.Name == player.Name then
print("Hello World", player.Name)
-- pass some data from the server to the client
RemoteEvent:FireClient( player, 1, 2, 3)
end)
end)
end)
Then in your client...
-- LocalScript in PlayerScripts
local ReplicatedStorage = game:GetService("ReplicatedStorage")
local RemoteEvent = ReplicatedStorage.RemoteEvent
-- since there's no telling when this event will fire, tell the server that we've loaded!
RemoteEvent:FireServer()
-- wait for the server to respond and give us some data
local connection
connection = RemoteEvent.OnClientEvent:Connect( function(a, b, c)
print("got data from server : ", a, b, c)
-- disconnect so this event only fires once
connection:Disconnect()
end)

Answer 2

I would like to add to Kylaaa's answer and in response to your code example that if your intention is to wait for a response from the client, you can also invoke a RemoteFunction instead of firing an event and waiting for an event to come back to you. Something like this:
Script:
game.Players.PlayerAdded:Connect(function(plr)
local response = game.ReplicatedStorage.RemoteFunction:InvokeClient(plr, "Hello")
print("Client said: " .. response)
end)
LocalScript:
game.ReplicatedStorage.RemoteFunction.OnClientInvoke = function(text)
print ("Server said: " .. text)
return "Hi"
end
PS. A RemoteFunction also works both ways.