Basic Networking Tool: netstat

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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

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List only TCP sockets

Use -t option to list only the TCP sockets.

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

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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 program name

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

netstat -lnp | grep 1234

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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.

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Note:

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

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

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