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I had VNC working great -- allowing access from both my Mac and my Windows laptop. I set it up from "Sharing" under the System Settings.

This morning nothing will connect.

The only thing that has changed on Ubuntu is that I was working to get the Mosquitto MQTT server running, and as part of that I enabled ufw so I could open port 1883. I was connected via VNC from both of my devices (i.e. Mac and Window 10 laptop) -- in fact I issued the ufw commands from the Windows 10 laptop VCN'd into the Ubuntu computer)

This morning is when nothing is connected or will allow connection. I'm not sure, does ufw need to have a VNC port added if it is running? If so, how do I determine which one to open?

Here is the output from ufw Status:

ufw Screenshot

MarkJoel60
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2 Answers2

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VNC uses port 5900 by default.

VNC by default uses TCP port 5900+N, where N is the display number (usually :0 for a physical display). source

If you block that with ufw (the default) you won't be able to connect.

Organic Marble
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You would be able to find more help on UFW here: Official guide to UFW

Please check out this official guide to have a better understanding of UFW and its commands. If still the issue persists, then I would request you to check your VNC setup once.

I corrupted my VNC configuration once and it took me days to identify it. To reconfigure my VNC setup, I took the help of these two guides:

Install and Configure VNC on Ubuntu 18.04 and, Installing VNC Server on Ubuntu OS

Sometimes, even the Firewall can be responsible for such errors. So, if you observe that the firewall is causing the issue. This guide highlighting Steps to Configure Firewall with UFW is your one-stop solution.

Thank you!

Regards

Manu Mathur
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