function receive(waitTime)
  if waitTime and type(waitTime) == "number" then
    local timer = os.startTimer(waitTime)
    while true do
      local event, timerEvent = os.pullEvent("timer")
      if timerEvent == timer then break end
      local event = {os.pullEvent("modem_message")}
      if event[3] == channel then
        return event[5], event[2]
      else
        print("Received nil")
      end
    end
  end
end