Navigating underneath a modal

Ionic Framework ionic-v3
1

Hi, I currently have an ionic app using WebSockets. After I create a modal, I would like for the pages underneath the modal to navigate to different pages depending on different WebSocket messages. Any idea for the best way to do that?

2 
let rootNav = this.app.getRootNavs()[0];
rootNav.setRoot(component, {}, navOptions); // or .push

This seems to work for me. Would there be any instances where getRootNavs()[0] would not return me the Nav underneath the modal?