Project

Fair enough question, but really too vague to answer. What do you mean by "project in developing a Firewall"? You want an example of a what could be a subtask? Like IDS, port binding, stateful inspection, pattern analysis, and allow/deny rule parsing?

No, that's not fair. You're asking others to do your job for you, without pay.

KerioKlone aims to be Windows 95/98/XP/2000 rule based firewall written in C/C++ with similar design and simplicity to but an improvement of Kerio Personal Firewall 2.15, a phased out closed source product. Note: This is not an official Kerio project!

And

Read for example the sourcecode of

- the Linux kernel and all the iptables stuff

- squid

- dante

- snort etc.

Wolfgang