In this tutorial we will show a basic technique for "port knocking". We
will be using some python code, ubuntu's firewall (ufw) and brain cells.
Any firewall can be used for this example but ufw was easily accessible and
easy to setup at the time. Lets look at the port knocking definition in the
wiki:
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port knocking is a method of externally opening ports on a firewall by
generating a connection attempt on a set of pre-specified closed ports.

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