Find number of unique IP's and active connections to Web server

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In computing, netstat (network statistics) is a command-line tool that displays network connections (both incoming and outgoing), routing tables, and a number of network interface (network interface controller or software-defined network interface) and network protocol statistics. It is available on Unix-like operating systems including OS X, Linux, Solaris, and BSD, and is available on Windows NT-based operating systems including Windows XP, Windows Vista, Windows 7 and Windows 8.
It is used for finding problems in the network and to determine the amount of traffic on the network as a performance measurement.
netstat is the most frequent tool used for monitoring network connections on a Linux servers. netstat returns a variety of information on active connections such as their current status, what hosts are involved, and which programs are involved. You can also see information about the routing table and even get statistics on your network interfaces. netstat is a good all-around utility and it is an essential tool for the Linux administrators.
If you just type netstat, it would display a long list of information that’s usually more than you want to go through at any given time. The trick is that how to keeping the information useful and what you’re looking for and how to tell netstat to only display that information.

Users can also use man netstat command to get detailed netstat help and manual where there are lots of configurable options and flags to get meaningful lists and results.

Contents 

• What is netstat?
• The Holy Grail of netstat – My way
  • Step 1: Show active connections – TCP and UDP Internet  (w/o servers)
  • Step 2: Show all active connections – (/w servers and established)
  • Step 3: Show all active connections to Web server
  • Step 4: Show all active connections to Web server excluding self IP’s
    • >> Sample output
  • Step 5: Show all active connections to Web server – IP: Port only
    • >> Sample output
  • Step 6: Show all active connections to Web server – IP’s only
    • >> Sample output
  • Step 7: Show all active connections to Web server – sorted and unique
    • >> Sample output
  • Step 8: Show all active connections to Web server – connection count
    • >> Sample output
  • Step 9: Show all active connections to Web server – exclude self IP’s
    • >> Sample output
  • Step 10: Final count of all active IP’s to Web server
    • >> Sample output
  • Step 11: Final count of all active connections to Web server
    • >> Sample output
• Conclusion
• Further helpful links, sources and references:
  • Google+
  • Related

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