Question How to List all current Open Ports on Plesk Obsidian

[MHC_1]

Server operating system version

AlmaLinux

Plesk version and microupdate number

Obsidian

Question is in the title.

I want to know How to list all current Open Ports on Plesk Obsidian ?

Currently I can see no way of informing me which ports are open and which are closed.

How can I also then open a custom port should I need to?

The only reference to "firewall" I can find in Plesk ; and implied by the Plesk documentation , is the Web Application Firewall which has no reference to Ports and looks very basic.

 

[MHC_1]

I have found terminal --> netstat -lntu instruction lists all open LISTENING ports.

I have not found how to change the status of any port.

 

[MHC_1]

How can I open a custom port on Plesk should I need to?

 

[Kaspar]

Install the Plesk firewall extension (if not installed already), after installation enable the firewall and create a rule to allow traffic on a specific port. By default on Almalinux firewalld is enabled and running, which can create conflicts with the Plesk firewall extension. Which is why it's recommend to stop and uninstall firewalld (via command line) when using the Plesk firewall extension.

 

[MHC_1]

Install the Plesk firewall extension (if not installed already), after installation enable the firewall and create a rule to allow traffic on a specific port. By default on Almalinux firewalld is enabled and running, which can create conflicts with the Plesk firewall extension. Which is why it's recommend to stop and uninstall firewalld (via command line) when using the Plesk firewall extension.

Thank you. `firewalld` is not installed. I am using the Plesk "Firewall" extension which creates a "firewall" button on the "Tools and Settings" menu, I have opened the port both incoming and outgoing and TCP/UDP but the connection to the port is refused for my remote connector.

 

[MHC_1]

Install the Plesk firewall extension (if not installed already), after installation enable the firewall and create a rule to allow traffic on a specific port. By default on Almalinux firewalld is enabled and running, which can create conflicts with the Plesk firewall extension. Which is why it's recommend to stop and uninstall firewalld (via command line) when using the Plesk firewall extension.

Further, running netstat -lntu I can see that the server is NOT listening on the ports defined in the firewall despite the firewall claiming their open. How do I get Plesk to actually establish a port is open to incoming or outgoing traffic?

 

[MHC_1]

AND I am finding that ports I blocked on the firewall (port 995 / POP3 port) are still in LISTEN mode on the linux terminal command. Why is the firewall being ignored?

 

[Kaspar]

I suspect you're mixing up a few thing. Applications are listening to (i.e using) ports for communication while a firewall on the other hand can allow or deny connections to and from ports. Those are different things. A port being open on a firewall does not mean that there is any application listing on the same port. The reverse is also true, an application listening on a specific port (or multiple ports) does not necessarily mean the port is actually open.

The netstat -lntu command shows which ports are being listen on, not which ports are open or closed by a firewall. That means, for example, that port 995 (POP3) can be listed as "listen" with the netstats command while the port is being blocked by a firewall.

Thank you. `firewalld` is not installed. I am using the Plesk "Firewall" extension which creates a "firewall" button on the "Tools and Settings" menu, I have opened the port both incoming and outgoing and TCP/UDP but the connection to the port is refused for my remote connector.

Perhaps there's another firewall in front of your server? It's quite common for (cloud) providers to offer a firewall you can manage in front of your server stack. It's also quite common for (cloud) providers to block certain ports by default (and only open them on request).

For troubleshooting purposes it's perhaps good to know that the Plesk firewall is just an user interface for iptables firewall. You can run iptables --line-numbers -nL to list all rules present in iptables (including those for the Plesk firewall). Disabling the Plesk firewall should leave your very few firewall rules in iptables.

 

[MHC_1]

@Kaspar thank you for you reply, yes I think my wording was imprecise.

upon closer investigation I think I have found that I had been editing the ssh_config not the sshd_config file as intended.

 

[MHC_1]

Also there was an issue that SELinux needed to be updated with the new port number and this was not done so the whole thing was failing by default. This issue is not mentioned at all on the Plesk documentation page linked above.