Door (door.lua)

--courtesy of Bomb Bloke
local function oc(state)
    redstone.setOutput("back", state)
    redstone.setOutput("front", state)
end

while true do
    if redstone.getInput("left") or redstone.getInput("right") then
        oc(false)
        os.pullEvent("redstone")  -- Yield until a redstone state change occurs.
    else
        oc(commands.exec("testfor @a[r=3]"))
        sleep(0.2)  -- Bigger sleep here = less server load, but less frequent checks.
    end
end