What does a rack handler do exactly?

Question

What does a rack handler do exactly, i.e. can someone explain in pseudo-code the steps that a rack handler takes to deliver a result for a request?

Answer 1

It processes the HTTP request headers and content, instantiating a Request object. It then passes the Request object through the middleware then to the rack application. The rack application instantiates a Response object and sends it back up through the middleware, and the hander turns it into HTTP response headers and content.