use Nginx as Reverse Proxy for WebSocket backends.

nginx-websocket-proxy.conf

# http {
map $http_upgrade $connection_upgrade {
    default upgrade;
    ''      close;
}

upstream local_origin {
    server localhost:5173;
    # I was using this for Vite HMR backend.
    # For Vite HMR ws proxy, see:
    #   https://github.com/sapphi-red/vite-setup-catalogue/blob/67b256a796486423caf4cfab396a99c186fcd1ab/examples/with-proxy/vite.config.js#L6-L12
}

server {
    listen 80;
    # listen 443 ssl;
    # ssl_certificate      server.crt;
    # ssl_certificate_key  server.key;
    # ssl_session_cache    shared:SSL:1m;
    # ssl_session_timeout  5m;

    location ~ {
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header X-Forwarded-Proto $scheme;
        proxy_set_header X-Forwarded-Host $host;

        proxy_pass http://local_origin;

        proxy_set_header Upgrade  $http_upgrade;
        proxy_set_header Connection $connection_upgrade;
        proxy_read_timeout 86400;
    }
}

# }

For Vite configuration, see:
https://github.com/sapphi-red/vite-setup-catalogue/blob/67b256a796486423caf4cfab396a99c186fcd1ab/examples/with-proxy/vite.config.js#L6-L12