Merge branch 'main' of ssh://gitlab.fdmci.hva.nl/propedeuse-hbo-ict/onderwijs/2023-2024/out-a-se-ti/blok-3/qaajeeqiinii59

docs/rpi-documentation/Reverse Proxy.md

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+### Reverse proxy
+
+
+#### Introduction
+A reverse proxy is for example used to host 2 services on the same port. This is useful for us because we can use the same port for the websockets and the webserver. 
+
+#### How to use a reverse proxy
+We are going to use `Apache2` as our reverse proxy. This is because it is easy to use and has a lot of documentation. It also hosts our webserver so it is easy to configure and we don't have to install another program.
+
+#### Additional modules
+We need to enable the `proxy` and `proxy_wstunnel` modules. These are used to proxy the websockets.
+
+You can install them with these commands on a Raspberry Pi. For other linux distributions its may be different.
+
+```bash
+$ sudo a2enmod proxy
+$ sudo a2enmod proxy_wstunnel
+```
+
+#### Script
+The enabled apache2 config scripts are found in `/etc/apache2/conf-enabled/`. You can create a new file with the name of your service. For example `studyarea.conf`.
+```apache
+<VirtualHost *:80>
+    DocumentRoot /home/pi/www/html/
+
+    # Enable proxying WebSockets
+    ProxyPass /ws ws://localhost:8001/
+
+    # Enable proxying HTTP
+    ProxyPass /ws http://localhost:8080/
+</VirtualHost>
+```
+Because VirtualHost is listening on port 80, we can use the same port for the webserver and the websockets. The `ProxyPass` is used to proxy the websocket. The `/ws` is the path where the websockets are hosted. Its hosted on `localhost/ws` so it kinda creates a new subdomain for the websocket. The `localhost:8001` is the address of the websockets and the `localhost:8080` is the address of the webserver.
+
+
+`DocumentRoot` is the path where the files are for the website.
+
+
+
+### Sources:
+
+* https://httpd.apache.org/docs/2.4/howto/reverse_proxy.html
+* https://www.serverlab.ca/tutorials/linux/web-servers-linux/how-to-reverse-proxy-websockets-with-apache-2-4/
+* https://gist.github.com/mortenege/91ec6fe02dca6f736303a00f8cea2731
+* https://www.jscape.com/blog/forward-proxy-vs-reverse-proxy#:~:text=While%20a%20forward%20proxy%20proxies,is%20providing%20file%20transfer%20services.
+* https://webmasters.stackexchange.com/questions/143106/functional-difference-between-proxypass-and-proxypassreverse-in-apache