[SOLVED] Ports not open even without firewall

Fedora 25, Gnome 3, two Core-i7 laptops with 8Gb and 1Tb.

This is probably the result of me not knowing as much as I would like about firewall-config and iptables, so please bear with me.

I have two machines. I want to control the desktop of A from B. Using firewall-config I set port 5900 and vnc-server to be open and available on A, but the port did not open after a reload and even after a reboot.

To test the results, I disabled firewalld.service and iptables.service on B and rebooted, expecting to find all my ports open in the absence of any firewall.

To my surprise, the only open ports are the same ones that were open beforehand.

I can control B from A via vinagre, so the network is not blocking anything.

I thought port opening/closing was controlled by the firewall. Please educate me as to what I have overlooked.

Kind regards,
Doug

A port will not show as open unless there is some process listening on that port.

Originally Posted by rknichols A port will not show as open unless there is some process listening on that port.

Well, there is something I didn't know - thank you very much for the information, which totally explains the problem I am seeing. It does not tell me how to fix it, but it does tell me where to start.

Just proves you are never too old to learn something new. "8-)

As rknichols hints, there are 4 options:

1. svc listening & firewall port open = access possible (may still need credentials)
2. svc listening & firewall port not open = no access possible
3. svc not listening & firewall port open = no access possible
4. svc not listening & firewall port not open = no access possible

You may want to install & use nmap tool

Originally Posted by chrism01 You may want to install & use nmap tool

Thanks chrism01. I have much to learn about networking and your comment has helped me along the way. "8-)

I have been learning a little about my ports with nmap, but was confused when it didn't show me the ports I had opened - it didn't occur to me nmap was only showing the ports with 'listeners'.

Cheers,
Doug

PS: Has anyone else had problems getting notification emails from the forum? I have set my options to get instant notifications, but have not received one for ages. "8-[
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Forget it: I just switched my email choice to Daily and back to Immediate, and emails started to come through again. Don't try to explain things like that - you'll upset the Software Gods.