Question Docker is fixing the Varnish configuration?

[lepe]

Hi

I have varnish test site blocked by ports and I dont understand what is set up wrong, when I check if varnish test site have cached HIT or MISS I receive error "503 Backend fetch failed". My Apache default port is 7080 and Nginx 80.
I set up varnish from setting port to 32780 from nginx port 80 in Docker following your guide https://talk.plesk.com/threads/varnish-for-wordpress-in-a-docker-container.342954/ and it shows good:

[root@localhost ~]# docker ps
CONTAINER ID        IMAGE               COMMAND                  CREATED             STATUS              PORTS                   NAMES
eaa7343c596c        million12/varnish   "/bin/sh -c /start.sh"   2 weeks ago         Up 35 hours         0.0.0.0:32780->80/tcp   varnish

But when I check varnish listen port it shows other ports:

[root@localhost ~]# netstat -nlp | grep varnish
tcp        0      0 0.0.0.0:6081            0.0.0.0:*               LISTEN      894/varnishd
tcp        0      0 127.0.0.1:6082          0.0.0.0:*               LISTEN      894/varnishd
tcp6       0      0 :::6081                 :::*                    LISTEN      894/varnishd

I added in /etc/varnish/default.vcl backend default { .host ="myIP" .port ="7080"}
NOTE: Varnish 5.1.2 + Centos 7.3 + Plesk Onix 17.5.3 + Apache 2.4.6

What is wrong?