hapi

local modem = peripheral.find("modem")

if not modem then
    error("No modems attached")
end

function closeAll()
    modem.closeAll()
end

closeAll()

function open(channel)
  if channel and channel >= 0 and channel <= 25565 then
     modem.open(channel)
    return true
  end
  return false
end

function send(channel, message)
  if not modem.isOpen(channel) then
    open(channel)
  end

  if channel and message then
    modem.transmit(channel, channel, message)
  end
end

function receive(channel, timeout)
  if not modem.isOpen(channel) then
    open(channel)
  end

  if timeout then
    time = os.startTimer(timeout)
  end

  while true do
    event = {os.pullEvent()}
    if event[1] == "modem_message" then
      return event[5]
    elseif event[2] == time then
        return "Timeout"
    end
  end
end