For the virtual machines like HortonWorks Sandbox (HDP) VM which is hosted on Oracle VirtualBox, we often deploy custom applications in the VM. This only brings a surprise later that this application is not accessible from Host machine, where as other standard hadoop ports like 8080, 8888, 4040 do open normally.
This trick here is that we need to enable Port Forwarding for the new ports we added in VirtualBox.
VM -> Devices -> Network -> Adapter -> Advances -> Click on Port Forwarding button -> Add Host port number and Guest Port numbers (these can be same though).
Here is the screenshot on where to update:
That's it. Now the application should be accessible from Host computer using the Host Port.