Apache reverse-proxy to NodeJS WebSocket Server - node.js

Question

Before all, yes I have checked other posts like this, this or even this among others.
This being said, let me expose my case:
It works on the dev-env (localhost) completely fine (of course, it doesn't require any proxy)
I also use this curl command to confirm:
curl 'http://localhost:9021/ws' \
--http1.1 \
-H 'Pragma: no-cache' \
-H 'Sec-WebSocket-Key: W/ZEACBv+gi6xA1JeMaO/A==' \
-H 'Upgrade: websocket' \
-H 'Cache-Control: no-cache' \
-H 'Connection: Upgrade' \
-H 'Sec-WebSocket-Version: 13'
and it connects ok.
When I run it on the remote dev server, I have this Apache config:
<IfModule mod_ssl.c>
<VirtualHost *:443>
ServerName dev.remote.com
LogLevel warn
ErrorLog "| /usr/bin/rotatelogs -l /home/user/log/dev.remote.com/error.%Y-%m-%d 86400"
CustomLog "| /usr/bin/rotatelogs -l /home/user/log/dev.remote.com/access.%Y-%m-%d 86400" combined
ServerSignature Off
DocumentRoot /home/user/www/dev.remote.com
<Directory /home/user/www/dev.remote.com>
Options -Indexes +FollowSymLinks +MultiViews
AllowOverride All
Require all granted
</Directory>
<Location />
Options FollowSymLinks
</Location>
#
# Serve static files directly with Apache
#
ProxyPass /public !
Alias /public /home/user/www/dev.remote.com/public
<Directory /home/user/www/dev.remote.com/public>
Options -Indexes +FollowSymLinks +MultiViews
AllowOverride All
Require all granted
</Directory>
ProxyPass /assets !
Alias /assets /home/user/www/dev.remote.com/.next/static/assets
<Directory /home/user/www/dev.remote.com/.next/static/assets>
Options -Indexes +FollowSymLinks +MultiViews
AllowOverride All
Require all granted
</Directory>
#
# Serve the rest with NodeJS/express
#
RewriteEngine On
LogLevel alert rewrite:trace6
RewriteCond %{HTTP:Connection} upgrade [NC]
RewriteRule /ws ws://localhost:9021/ws [P]
ProxyPreserveHost On
ProxyRequests off
# WebSocket server (express) is on port 9021
ProxyPass /ws ws://localhost:9021/ws
ProxyPassReverse /ws ws://localhost:9021/ws
# HTTP server (express) is on port 9020
ProxyPass / http://localhost:9020/
ProxyPassReverse / http://localhost:9020/
<Proxy *>
Require all granted
</Proxy>
SSLCertificateFile /etc/letsencrypt/live/dev.remote.com/fullchain.pem
SSLCertificateKeyFile /etc/letsencrypt/live/dev.remote.com/privkey.pem
Include /etc/letsencrypt/options-ssl-apache.conf
</VirtualHost>
</IfModule>
So 2 points here:
1.
I'm sure the WebSocket server is working on the remote server by testing via ssh with the previous curl command. And it connects.
2.
When I try opening the connection from the browser
ws = new WebSocket('wss://dev.remote.com/ws');
the mod_rewrite rule seems ok because the trace is like this:
[Fri May 28 17:37:16.272448 2021] [rewrite:trace2] [pid 15772] mod_rewrite.c(477): [client a.b.c.d:63015] a.b.c.d - - [dev.remote.com/sid#6916462d1a20][rid#69164d3530a0/initial] init rewrite engine with requested uri /ws
[Fri May 28 17:37:16.272475 2021] [rewrite:trace3] [pid 15772] mod_rewrite.c(477): [client a.b.c.d:63015] a.b.c.d - - [dev.remote.com/sid#6916462d1a20][rid#69164d3530a0/initial] applying pattern '/ws' to uri '/ws'
[Fri May 28 17:37:16.272505 2021] [rewrite:trace4] [pid 15772] mod_rewrite.c(477): [client a.b.c.d:63015] a.b.c.d - - [dev.remote.com/sid#6916462d1a20][rid#69164d3530a0/initial] RewriteCond: input='Upgrade' pattern='upgrade' [NC] => matched
[Fri May 28 17:37:16.272513 2021] [rewrite:trace2] [pid 15772] mod_rewrite.c(477): [client a.b.c.d:63015] a.b.c.d - - [dev.remote.com/sid#6916462d1a20][rid#69164d3530a0/initial] rewrite '/ws' -> 'ws://localhost:9021/ws'
[Fri May 28 17:37:16.272521 2021] [rewrite:trace2] [pid 15772] mod_rewrite.c(477): [client a.b.c.d:63015] a.b.c.d - - [dev.remote.com/sid#6916462d1a20][rid#69164d3530a0/initial] forcing proxy-throughput with ws://localhost:9021/ws
[Fri May 28 17:37:16.272529 2021] [rewrite:trace1] [pid 15772] mod_rewrite.c(477): [client a.b.c.d:63015] a.b.c.d - - [dev.remote.com/sid#6916462d1a20][rid#69164d3530a0/initial] go-ahead with proxy request proxy:ws://localhost:9021/ws [OK]
So I deduct the rules are working and it's actually making the request via proxy to :ws://localhost:9021/ws
But... there's no connection received in the WebSocket server.
Therefore, I get this on Chrome:
WebSocket connection to 'wss://dev.remote.com/ws' failed

Answer 1

The key was to have proxy_wstunnel mod active >_<
In case it helps anyone...
cd /etc/apache2/mods-enabled
sudo ln -s ../mods-available/proxy_wstunnel.load
stupid error, but I was too focused on the configuration, and it was about enabled mods