It is a common shell script, what was created with the study goals.
Sometimes you need to open ports to some hosts for the short time.
The  script would automate this action for you with default Linux
firewall netfilter via iptables.

It is very simple to use it/
Copy file to the directory /bin or /usr/bin, make it executable, 
set the defaults in the script (host, port, time, proto) and run:
and run:

openport.sh open 

In this example script uses defaults.
Or this:

openport.sh open --host 192.168.123.31 --port 80 proto tcp --sleep 10

Script opens tcp-port 80 (www) to the host 192.168.123.31 for the
10 minutes, after this period it closes port and ends its work.