How can I use Android "remotes" when outside of my home network when using a VPN?

Question

I recently downloaded Transdroid (Transdrone) and started using it. It is an app that allows me to operate Transmission on my desktop from my phone.

I was able to get it to connect properly while connected to my home network via wifi. As usual, I wanted to push the envelope a bit and try to get it to connect when I am using my 4G connection. So I determined my external IP, enabled port forwarding on the proper port, and viola! Connected.

However, when I connect to my VPN (ExpressVPN via OpenVPN), the connection fails. So I determined "my" external IP when connected to the VPN, configured it in the app, and still could not get it to connect.

This was not a surprise really... I know a tiny bit about how these things work, however I do not know what I need to do to successfully use the android remote when connected via VPN.

I assume since I had to enable forwarding on that certain port on my router, something similar would need to be done on my VPN server. ExpressVPN does not have anyway for me to configure port forwarding on that end...

Even if I could port forward on my VPN, I'm not sure if that would defeat the purpose of the VPN completely (make my P2P sharing activities and true IP known to Comcast). Will it?

So my question: How can I use apps like this (android remotes) when out and about (not connected to my home network) while using a VPN?

Answer 1

I ended up using AirVPN remote port forwarding via their control panel. No port forwarding was done on my router.

I configured two ports (port 41000 & 42000), configured my firewall to allow incoming connections on my machine (no need to allow outbound since my firewall allows outgoing) via port 41000 and 42000, then launched the programs that would use those ports. In this case: Transmission.

With those ports configured in Transmission's settings, I headed to http://whatismyip.com and determined my external IP when connected to the VPN.

I had to click the 'check' button on AirVPN's site at this time to verif port activity. A green light was displayed, thus I was ready to attempt connecting.

I then launched my remote app on my phone, set the app to connect to that external IP via port 41000 and 42000. Voila!

Hope this helps somebody. I can elaborate further if needed :)