From mboxrd@z Thu Jan  1 00:00:00 1970
From: "Adem" <for-gmane@alicewho.com>
Subject: Allow client only 1 connect per 20 seconds
Date: Tue, 25 Nov 2008 19:38:38 +0100
Message-ID: <gghgq9$33t$1@ger.gmane.org>
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How would you code this rule in iptables:

If anybody tries to do more than 1 connection to port 8191
within 20 seconds, regardless of the protocol, then DROP 
it and ignore any further connect attempts on that port
from that source for 20 seconds.