ServerScriptService.Script:4: attempt to index nil with 'UserId' Can Somebody Help Me?

So I have an error in my code. I have been trying to give all players a hat when they spawn however I get an error for some reason. I would really appreciate it if you could help me.

I get this error: ServerScriptService.Script:4: attempt to index nil with 'UserId' Script 'ServerScriptService.Script', Line 4

Anyways this is my code:

	local players = game:GetService("Players")
	local serverStorage = game:GetService("ServerStorage")

	local users = players.LocalPlayer.UserId

	local isAllowed = function(player, tab)
	for i, v in pairs(tab) do
		if player.UserId == v then return true end
	end
	return false
	end

	players.PlayerAdded:Connect(function(player)

		player.CharacterAdded:Connect(function(character)
		local hat = serverStorage:WaitForChild("Combat Helmet") 
		if isAllowed(player, users) then
			local clone = hat:Clone()
			clone.Parent = character
		end
	end)

end)

Simple.

The server can not use LocalPlayer as it is never defined only local scripts can use it

Also if your trying to get all the players you need a table not a userid.

Your code should look something like this:

    local players = game:service("Players") -- or :GetService('Players')
    local serverStorage = game:service("ServerStorage") -- or :GetService('ServerStorage')

    local users = players:players() -- or :GetPlayers()

    local isAllowed = function(player, tab)
    for i, v in pairs(tab) do
        if player.UserId == v then return true end
    end
    return false
    end

    players.PlayerAdded:Connect(function(player)

        player.CharacterAdded:Connect(function(character)
        local hat = serverStorage:WaitForChild("Combat Helmet") 
        if isAllowed(player, users) then
            local clone = hat:Clone()
            clone.Parent = character
        end
    end)

end)