Q: Docker-based Func App unable to connect with servers in VNet

I'm trying to make a serverless Function App to connect to a server in my VNet.

I've created a Function App based on a custom docker image as per [this tutorial](https://docs.microsoft.com/en-us/azure/azure-functions/functions-create-function-linux-custom-image).

Then I connected that Function App to a VNet, where I have a VM running an application with a REST API.

In the Function App I had function that used Python requests package to connect to that VM. The code worked in my local testing, but returned me "Connection refused" error when I ran the function in the cloud.

I've read the bit on PORT variable, but it seems to be not applicable in my case, because my docker app acts as a client in this case. Is there any other troubleshooting I can do, or this setup is just not supported?