Add Occupy A Local Port With Netcat as a Unix TIL

README.md

@@ -10,7 +10,7 @@ pairing with smart people at Hashrocket.
 
 For a steady stream of TILs, [sign up for my newsletter](https://crafty-builder-6996.ck.page/e169c61186).
 
-_1237 TILs and counting..._
+_1238 TILs and counting..._
 
 ---
 
@@ -1213,6 +1213,7 @@ _1237 TILs and counting..._
 - [List The Available JDKs](unix/list-the-available-jdks.md)
 - [List The Stack Of Remembered Directories](unix/list-the-stack-of-remembered-directories.md)
 - [Map A Domain To localhost](unix/map-a-domain-to-localhost.md)
+- [Occupy A Local Port With Netcat](unix/occupy-a-local-port-with-netcat.md)
 - [Only Show The Matches](unix/only-show-the-matches.md)
 - [Open The Current Command In An Editor](unix/open-the-current-command-in-an-editor.md)
 - [Partial String Matching In Bash Scripts](unix/partial-string-matching-in-bash-scripts.md)

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

@@ -0,0 +1,20 @@
+# 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.
+
+```bash
+$ 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.
+
+[source](https://twitter.com/jbrancha/status/1566820110366654474?s=20&t=HcUMm1aRXpEgCAzONhy34w)