Port Knocking with iptables

After I implemented the port knocking using the code from Zeroflux (see my earlier post on Port Knocking) I discovered that actually I could have done the same with iptables. However, I was too busy with work to go and change the to iptables based solution. Today I wanted to do port knocking for another machine and so decided to investigate the iptables based solution. Turns out it is just 2 lines of iptables. Thanks Daniel de Graff for the link.