Show an example UPnP request with double NAT

I write in C ++ Qt a peering chat (signaling servers are not assumed, the network is completely distributed). How can I send a request for port forwarding to the provider's router from the client software code to UPnP? Be sure to show sample code. And then the second question on the same subject: according to statistics, 80% of ordinary users are sitting behind a double NAT, i.e. the first one brings to the internal network of the provider, and the second one - to the outside world, and so - show how to programmatically send a UPnP request to both these NATs to break through the path of peering communication through them.