connect() failed (111: Connection refused) while connecting to upstream

It sounds like you haven’t started and configured the backend for Nginx. Start php-fpm and add the following to nginx.conf, in the http context:

server {
    listen 127.0.0.1;
    server_name localhost;

    error_log /var/log/nginx/localhost.error_log info;

    root /var/www/localhost/htdocs;

    location ~ \.php$ {
        fastcgi_pass 127.0.0.1:9000;
        include /etc/nginx/conf.d/*.conf;
        include /etc/nginx/sites-enabled/*;

        fastcgi_intercept_errors        on;
        error_page 404 /error/404.php;
    }
}