Thank you all for the help, did.

Debian GNU/Linux Jessie:

sudo service nginx stop

Code:

server {
listen 80;

server_name forum.mydomainname.ru;

location / {
    proxy_set_header X-Real-IP $remote_addr;
    proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
    proxy_set_header X-Forwarded-Proto $scheme;
    proxy_set_header Host $http_host;
    proxy_set_header X-NginX-Proxy true;

    proxy_pass http://127.0.0.1:4567/;
    proxy_redirect off;

    # Socket.IO Support
    proxy_http_version 1.1;
    proxy_set_header Upgrade $http_upgrade;
    proxy_set_header Connection "upgrade";
}

}

You need to paste the code in:
/etc/nginx/sites-enabled/default

sudo service nginx start

Thanks @PitaJ I forgot to clarify.
I use http://www.cloudflare.com as DNS.
I have recorded a cloudflare DNS record.
I don't use https, only http.

Please tell me how to make what my website did not work http://ip:4567/ a http://forum.mydomainname.ru/

I have the following settings:
{
"url": "http://forum.mydomainname.ru",
"secret": "censor",
"database": "mongo",
"port": 4567,
"mongo": {
"host": "127.0.0.1",
"port": "27017",
"username": "censor",
"password": "censor",
"database": "censor"
}
}

nginx, apache httpd is not installed.
VPS, Debian GNU/Linux Jessie. Linux 3.6.x
NodeBB 1.4.2
Installed only NodeJS, MongoDB

Please explain how that would make my site work as http://forum.mydomainname.ru/