Port-Accountant
Easily find out what servers are attempting to connect to your service (port).
Its as easy as
./paccount.sh 80
The following 3 hosts have connected to port 80 of www.hellspark.com since Fri Oct 30 13:46
crawl-66-249-65-124.googlebot.com(66.249.65.124)
msnbot-157-55-39-12.search.msn.com(157.55.39.12)
s420.pingdom.com(72.46.130.42)
The program will continue to run updating the list above until canceled...