Access node app on digital ocean - This site can't be reached

Some Digital Ocean droplets (mainly one-click apps) come with ufw firewall installed and by default all ports except for 22, 80, and 443 are blocked.

To check if ufw is installed and which ports are blocked/open do:

sudo ufw status

Output:

To                         Action      From
--                         ------      ----
22                         LIMIT       Anywhere                  
80                         ALLOW       Anywhere                  
443                        ALLOW       Anywhere                  
22 (v6)                    LIMIT       Anywhere (v6)             
80 (v6)                    ALLOW       Anywhere (v6)             
443 (v6)                   ALLOW       Anywhere (v6)

To allow traffic on port 9000 do:

sudo ufw allow 9000/tcp