NOOP - No Operation
We have just about come to the end of this tutorial, we have yet to look at Active Mode data transfer and will forget that for the moment. We will conclude by taking a quick look at 'NOOP'
NOOP does nothing. In fact it stands for NO Operation. So what's the use of it? well it helps you keep your connection alive during periods of inactivity.
With single threaded file transfer programs such as our web based client there will be no communications over the control connection when large files are being uploaded or downloaded. FTP servers are configured to kick off idle connections after a period of inactivity. This is around 5 minutes on most servers but could be as low as a minute for very active download sites.
Using NOOP allows us to make sure that commands are passed over the control connection without changing the status of any data transaction or server status. It can also be used as a harmless way of detecting timeouts.
Let's get onto the last demo.