I don’t understand what the problem is. I tried so many things! This is error what i get!

2021/02/06 01:07:00 [error] 728#728: *1 connect() failed (111: Connection refused) while connecting to upstream, client: 77.219.0.204, server: domens.lv, request: "GET /socket.io/?EIO=4&transport=polling&t=NTqu5wj HTTP/1.1", upstream: "http://127.0.0.1:3000/socket.io/?EIO=4&transport=polling&t=NTqu5wj", host: "domens.lv", referrer: "https://domens.lv/"

Here is my Nginx default

server {

    root /var/www/html;

    # Add index.php to the list if you are using PHP
    index index.html index.htm index.nginx-debian.html;

    server_name domen.lv.lv www.domen.lv.lv;

        location /socket.io/ {
            proxy_http_version 1.1;
            proxy_set_header Upgrade $http_upgrade;
            proxy_set_header Connection "Upgrade";
            proxy_set_header Host $host;
            proxy_pass http://localhost:3000/socket.io/;
        }

    location / {
        # First attempt to serve request as file, then
        # as directory, then fall back to displaying a 404.
        proxy_pass http://localhost:3000;
                proxy_http_version 1.1;
                proxy_set_header Upgrade $http_upgrade;
                proxy_set_header Connection 'upgrade';
                proxy_set_header Host $host;
                proxy_read_timeout 96000;
                proxy_cache_bypass $http_upgrade;
               }

                listen [::]:443 ssl ipv6only=on; # managed by Certbot
                listen 443 ssl; # managed by Certbot
                ssl_certificate /etc/letsencrypt/live/hola.lv/fullchain.pem; # managed by Certbot
                ssl_certificate_key /etc/letsencrypt/live/hola.lv/privkey.pem; # managed by Certbot
                include /etc/letsencrypt/options-ssl-nginx.conf; # managed by Certbot
                ssl_dhparam /etc/letsencrypt/ssl-dhparams.pem; # managed by Certbot
}

server {
    if ($host = www.domen.lv.lv) {
        return 301 https://$host$request_uri;
    } # managed by Certbot


    if ($host = domen.lvlv) {
        return 301 https://$host$request_uri;
    } # managed by Certbot


    listen 80 default_server;
    listen [::]:80 default_server;

    server_name domen.lv www.hola.lv;
    return 404; # managed by Certbot
}

script.js

// connect to main namespace const socket = io('/');

const conversation = document.querySelector('.conversation');

let alreadyTyping = false;

// change the number of online

nginx.conf

user www-data;
worker_processes auto;
pid /run/nginx.pid;
include /etc/nginx/modules-enabled/*.conf;

events {
    worker_connections 768;
    # multi_accept on;
}


http {


    sendfile on;
    tcp_nopush on;
    tcp_nodelay on;
    keepalive_timeout 65;
    types_hash_max_size 2048;

    include /etc/nginx/mime.types;
    default_type application/octet-stream;

    ssl_protocols TLSv1 TLSv1.1 TLSv1.2 TLSv1.3; # Dropping SSLv3, ref: POODLE
    ssl_prefer_server_ciphers on;

    access_log /var/log/nginx/access.log;
    error_log /var/log/nginx/error.log;

    gzip on;


    include /etc/nginx/conf.d/*.conf;
    include /etc/nginx/sites-enabled/*;
}

index.html

  <script src='/socket.io/socket.io.js'></script>
    <script src='./script.js'></script>