How to get mapping of browser and native host launched through extension launched from an application?

Question

Suppose an application launches a browser which in turn launches a native messaging host through an extension. After that, say, application needs to communicate with the native host which in turn can talk to the browser. I have a couple of questions on this

1. What is the best way to achieve this?
2. If the application ends up launching multiple browsers, how does application know to communicate with the right host program to send information to the right browser?

~ Nathan