Open port on ubuntu 16.04/20.04 LTS

 Open terminal [ctrl+T] and hit 

sudo ufw status

Apache Full                ALLOW       Anywhere
22                         ALLOW       Anywhere
3306                       ALLOW       161.202.20.0/24
3306 on eth1               ALLOW       Anywhere
3306                       ALLOW       Anywhere
Apache Full (v6)           ALLOW       Anywhere (v6)
22 (v6)                    ALLOW       Anywhere (v6)
3306 (v6) on eth1          ALLOW       Anywhere (v6)
3306 (v6)                  ALLOW       Anywhere (v6)

There is no 8080 port in above list

Now allow 8080 port 

sudo ufw allow