til/unix/occupy-a-local-port-with-netcat.md

Occupy A Local Port With Netcat

The netcat (nc) utility can listen to a specific port on your local machine. This, in effect, occupies that port. This is handy for a variety of reasons. In my case, I find it useful for testing out a web server script that can gracefully react to its desired port being occupied.

The -l flag is how you tell nc to listen. Then you specify localhost as the host and whatever port you want to occupy after that.

$ nc -l localhost 5000

Now if I try to run my web server script for port 5000, I see the Address already in use error.

See nc -h for more details.

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