This is a long shot, but I thought I'd give it a go, just in case anyone knows how to do this.

So, I have a device that can stream live video in multiple formats. This device can access and connect to a wifi network and start streaming.

Now I want to be able to take this device (HOST) with me to a remote location and if there is 3G /4G signal, hook the device up to my Android mobile via tethering and stream live. So far I have achieved that, by streaming (rtsp) to a service like Youtube or Facebook live. Essentially the device talks to the server, initiates a communication and starts the stream.

Now what I want to do is use the same scenario as above, but instead of streaming to a service, just be able to connect to the device from another point (CLIENT) which is in a totally different network and view the stream. My limited networking understanding thinks that that entails forwarding a port to the host and accessing it via IP/port from the client. However the host is behind a tethered mobile connection, which complicates things quite a bit.

What I am thinking is... Is there a service that can talk to these 2 devices and help connect them up so they can start the stream? Something like the way Skype works?

Or is there a manual way of doing any port forwarding on the Android device?

Thanks heaps in advance for any kind of advice :)