VBox Cannot VNC from Ubuntu host to CentOS guest

[padmahasa]

Hello,

I'm not sure whether it is the issue with CentOS or Virtualbox.
I'm unsuccessful trying to VNC from Ubuntu host to CentOS guest. However I've installed another guest Ubuntu 18.04.1 and I can VNC into that OS without any issue. I've enabled "Sharing" in Settings and I tried both "Password" method and "New connections must ask for access" method. Both are not working.

One more observation is, when trying with "Password" method, the password I entered is not saved when I check back after restarting CentOS or at some situation, even in the same session.

Below are the Software specifications.
VirtualBox 6.0.14
(Host) Ubuntu 18.04.3
(Guest) CentOS 8
(VNC client) Remmina

Please suggest me to diagnose this issue. Is there is any way I can find in CentOS, information related to rejecting the connection?

Thank you.

[BShT]

look at your firewall rules

[KernelOops]

Maybe your connection is blocked due to the virtualbox internal NAT? Have you tried to set the vbox ethernet to bridged mode?

[padmahasa]

look at your firewall rules

Hello BShT,

I've not messed up with firewall, unless it's blocked, by default in CentOS 8. Below are the output of some firewall related commands I found on Redhat docs.

Commands and Output
firewall-cmd --state
running

firewall-cmd --list-all
public (active)
target: default
icmp-block-inversion: no
interfaces: enp0s3
sources:
services: cockpit dhcpv6-client ssh
ports:
protocols:
masquerade: no
forward-ports:
source-ports:
icmp-blocks:
rich rules:

firewall-cmd --list-all --zone=home
home
target: default
icmp-block-inversion: no
interfaces:
sources:
services: cockpit dhcpv6-client mdns samba-client ssh
ports:
protocols:
masquerade: no
forward-ports:
source-ports:
icmp-blocks:
rich rules:

In Ubuntu Gnome, just by enabling sharing with password, worked flawlessly. So I did the same in CentOS Gnome too.
Is there is any additional steps I should follow in CentOS 8 to get VNC work?

Thank you.

[padmahasa]

Maybe your connection is blocked due to the virtualbox internal NAT? Have you tried to set the vbox ethernet to bridged mode?

Hello KernelOops,

I've setup Bridged adapter and SSH connection from both regular terminal and Remmina is also working flawlessly.
If SSH is successful, there should be no issue with the establishing connection right?
In Ubuntu (18.04.1) which also uses Gnome DE (Another VM), I just enabled sharing with password and it worked without issues. So I did the same here for CentOS 8 which uses Gnome as it's default DE.
Do I need to do any additional setup to get VNC working here?

Thank you.

[BShT]

you don´t have vnc service or port listed in your firewall

[KernelOops]

As BShT mentioned above, it seems your firewall is blocking vnc, because there are no service/port entries in your home zone.

[padmahasa]

you don´t have vnc service or port listed in your firewall

Can you please tell me what is the service name of VNC in CentOS?

Thank you.

[BShT]

https://www.redhat.com/sysadmin/secure- ... rewall-cmd

[KernelOops]

I have no idea, I don't use VNC.