Debian VM, firewall blocking external PHP accessing NodeRed App on port 30300, Android App works OK

[pctborges]

I have a Node-Red App that works as an API responding to http requests on port 30300.

The App URL is: http://alprbr.com:30300/alprbr.

External App submits (using http POST) some parameters and, in return, should get a JSON response.

Android App running on my smartphone works OK.

Some other server running PHP submits http POST to Node-Red on port 30300 and gets no response.

Node-Red console reports no access at all.

Installed PHP App on the same server as Node-Red (Debian VM) and changed target server from external address to http://127.0.0.1:30300/alprbr  and PHP gets the JSON response successfully.

I also have another APP developed on C++ running in a microcontroller and accessing the same API and it works OK as well.

What might I be doing wrong?

Thanks

Paulo

[Shikar]

Can you please advise what kind of VM image you are using and would you be able to provide the playbook or documentation you are following for your particular Application setup. That would help me to investigate further. 

Thank you.