As of right now (2018) what is the http/tcp server used when you set up a luminus template project with its default setting? 

I'm reading that luminus uses immutant, however, immutant is a collection of other stuff. and I've also read that the underlying server used in immutant is undertow. 

Am I correct in assuming that the default server is undertow? If so, how does the default set up perform with respect to non-blocking IO? Does this server afford a non-blocking event loop architecture like nginx/nodejs?