On Ubuntu 20.04 how do you open a port in the firewall

Question

Googled and found nothing recent. I did find docs on ufw and I ran:

thomas@Westeros:~/git/heavyweight-software$ sudo ufw status verbose
[sudo] password for thomas: 
Status: inactive

So I'm thinking it isn't running ufw anymore. I can ping my computer, but I can't connect to it on my development web server port 4200. Can't find any docs on ubuntu site either.

Solution

Finally found the answer here: https://www.cyberciti.biz/faq/how-to-configure-firewall-with-ufw-on-ubuntu-20-04-lts/

The answer appears to be that ufw is disabled by default and there is a default policy in place that doesn't use that. So I ran:

sudo ufw enable

And then ran

sudo ufw allow 4200

now sudo ufw status verbose returns me the information I wanted to see.

Additionally, https://stackoverflow.com/questions/43492354/how-to-allow-access-outside-localhost taught me to run ng serve --host 0.0.0.0 to serve my angular app outside of localhost.

Comments

[Thom]

Let me try again. When I run ufw status verbose it says status: inactive, which tells me that ufw is not my firewall. Running the allow 4200 command accomplished nothing and the status still says inactive.

[KilianAlias]

Ah I see. Are you connecting through LAN or the internet, as you will need to portforward if you are connecting over the internet.

[Thom]

I am connecting over a LAN.

[KilianAlias]

UFW is the default firewall application. You could try enabling it and adding a rule, but other than that I am not sure.