docs: update port example (#3391)

Author: snitin315

examples/cli/host-and-port/README.md

@@ -3,46 +3,79 @@
 You may choose to wish to change the host and port on which `webpack-dev-server`
 will run. The `host` and `port` options allow for that.
 
-## IPv4
+## host
+
+### IPv4
 
 ```console
 npx webpack serve --open-target --port 5000 --host 0.0.0.0
 ```
 
-## IPv6
+### IPv6
 
 _This also works with IPv6_
 
 ```console
 npx webpack serve --open-target --port 5000 --host ::
 ```
 
-## local-ip
+### local-ip
 
 Specifying `local-ip` as `host` will try to resolve the `host` option as your local `IPv4` address if available, if `IPv4` is not available it will try to resolve your local `IPv6` address.
 
 ```console
 npx webpack serve --open-target --port 5000 --host local-ip
 ```
 
-## local-ipv4
+### local-ipv4
 
 Specifying `local-ipv4` as `host` will try to resolve the `host` option as your local `IPv4` address.
 
 ```console
 npx webpack serve --open-target --port 5000 --host local-ipv4
 ```
 
-## local-ipv6
+### local-ipv6
 
 Specifying `local-ipv6` as `host` will try to resolve the `host` option as your local `IPv6` address.
 
 ```console
 npx webpack serve --open-target --port 5000 --host local-ipv6
 ```
 
-## What Should Happen
+#### What Should Happen
 
 1. The script should open `http://0.0.0.0:5000/` if specifying the IPv4 option,
    or `http://[::]:5000/` for IPv6, in your default browser.
 2. You should see the text on the page itself change to read `Success!`.
+
+## port
+
+### specific port
+
+Tell the server to connect to a specific port with the following:
+
+```console
+npx webpack serve --open-target --port 9000
+```
+
+#### What Should Happen
+
+1. The script should open `http://localhost:9000/` in your default browser.
+2. You should see the text on the page itself change to read `Success!`.
+
+### auto
+
+Specifying `auto` as `port` will try to connect the server to the default port `8080` and if not available it will automatically search for another free port.
+
+```console
+npx webpack serve --open-target --port auto
+```
+
+#### What Should Happen
+
+1. The script should open `http://localhost:8080/` in your default browser.
+2. You should see the text on the page itself change to read `Success!`.
+3. Keep the server open and switch to a new terminal window.
+4. Run the script once again.
+5. The script should open `http://localhost:8081/` (or any other port if it is not free) in your default browser.