Basic Networking Tool: netstat

netstat is a command-line networking tool, which can be used to show the statistics of networking connections. It’s a must tool for finding the performance problems in Unix/Linux networking.

In this post, I will list the typical usages and most used options of netstat.

List all the sockets

Use -a option to list all the sockets, including those in listen state and also not in listen state.

Use -l option to list the sockets in listen status.

netstat -a

List only TCP sockets

Use -t option to list only the TCP sockets.

netstat -tnetstat -lt # list all TCP sockets in listen status

Find the related process

Use -p option to show the program name and pid with sockets.

netstat -ltp # list all TCP sockets in listen status, with the program name

Suppose we want to find which process is binding a specific socket.

netstat -lnp | grep 1234

Use pipeline for statistics of networking

With the pipeline, we could combine netstat with other command utilities, like awk, sort.

Let’s find all the counts for different networking status.

Note:

awk '{print $6}' : use just the 6th column from the output.

tail -n + 2 : remove the first line from output (since it’s a header)

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