netstat -antu | grep :80 | grep -v LISTEN | awk '' | cut -d: -f1 | grep -v 127.0.0.1 | wc -l So, let’s try to list the 5th field which contains all the foreign IP addresses. awk has the capability to do data extraction. ![]() In the above line, I am only interested on the foreign IP 202.28.177.61. Let’s look at a sample output from previous command. awk is exactly the tool I need to use here. I want to exclude everything and only list foreign IP addresses. Step 5: Show all active connections to Web server – IP: Port only netstat -antu | grep :80 | grep -v LISTEN > Sample output # netstat -antu | grep :80 | grep -v LISTEN So I will just use grep -v to exclude these connections. I am more interested to see foreign IP’s connected to my website. I don’t want to exclude that as it is just loopback address. But I can see few entries like following: tcp 0 0 0.0.0.0:80 0.0.0.0:* LISTEN So far I managed to list all active TCP and UDP connections and filter my results for port 80. Step 4: Show all active connections to Web server excluding self IP’s You can use netstat -anu to list UDP connections. (in fact it will be all TCP as HTTP is a TCP service). Nice, now I see active TCP and UDP Internet connections on port 80 only. I want to narrow it down to port 80 only (HTTP Port). In this particular output, I got all sorts active TCP and UDP Internet connections on every open port. Now that I have a decent output, I can start working on it. Step 3: Show all active connections to Web server ‘ -a ‘ already includes everything, ‘ -l ‘ is not required. I’ve seen way too many guides where people go an use ‘ plan ‘ flag. antu = All TCP and UDP connections in numeric order (with servers and established) So I will just add ‘ -a ‘ flag in this command. If it does, then I got either mis-configured services or my server is compromised. But how do I know what ports I am listening to? I need that cause I want to check that my server is not listening to any funky ports. Step 2: Show all active connections – (/w servers and established) ntu = TCP and UDP connections in numeric order (w/o servers). I will break down each command as I go: Step 1: Show active connections – TCP and UDP Internet (w/o servers)įirst of all lets just check the active TCP and UDP connections. I don’t want to see my own server’s IP in the outputįollowing commands will do just that.I want to see total number of connections per IP.I only want to see users on port 80 (http).I want to see all users connected to my server.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. 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. 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. netstat is a good all-around utility and it is an essential tool for the Linux administrators. You can also see information about the routing table and even get statistics on your network interfaces. netstat returns a variety of information on active connections such as their current status, what hosts are involved, and which programs are involved. Netstat is the most frequent tool used for monitoring network connections on a Linux servers. It is used for finding problems in the network and to determine the amount of traffic on the network as a performance measurement. ![]() ![]() 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. 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.
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