Since most useful network conversations have two sides, stateless packet filters need two rules for each kind of network traffic they allow--one for the request and another for the reply.

iptables: A user-space utility to configure the Linux kernel firewall implemented by Netfilter. It allows users to define rules for packet filtering, NAT, and packet mangling. Practical Examples ...

I'm tired of messing with FreeBSD an Linux trying to get a packet filtering firewall going.<P>So until I figure out anything better, I'll give w2k a whirl. <P>Microsoft has proxy server 2.0, but I ...