How to set up UPnP Remote Access service?

I am setting up an application where I have to remotely control a device (switch) from another network. I learned from my research that this can be done using UPnP . I have implemented a code for a local network that is capable of controlling a device on the same network. But when I change the network, I cannot do it. I went through the UPnP forum pdf and got a theoretical understanding of the remote access implementation. But I didn't get any sample code for the same programming language. Does anyone have any sample code for this or at least can anyone suggest me how I can achieve this?