How to access web app in internal network on ubuntu

A web application is running on ubuntu machine on port 7777.

I am trying to access this web app in internal network.

I have tried to open port using:

sudo ufw allow 7777/tcp

and I get relevant status

 To                         Action      From
--                         ------      ----                      
22/tcp                     ALLOW       Anywhere                  
7777                       ALLOW       Anywhere                   
22/tcp (v6)                ALLOW       Anywhere (v6)             
7777 (v6)                  ALLOW       Anywhere (v6)   

still I can not reach the app through internal network.

I also changed this config net.ipv4.ip_forward=1.

What can be done to share localhost web apps through internal network.

p.s. ssh works fine. Host machine can connect virtual linux through ssh.