[undertow-dev] what I do wrong?

Hello guys, could you help me a little bit with Undertow? I follow all instructions in Undertown's poor documentation. So here is the class : public class HelloWorldServer { public static void main(String... args) { Undertow server = Undertow.builder() .addHttpListener(8080, "localhost") .setHandler(new HttpHandler() { @Override public void handleRequest(final HttpServerExchange exchange) throws Exception { if (exchange.isInIoThread()) { System.out.println("Thread #" + Thread.currentThread().getName() + " is I/O : handle this"); exchange.dispatch(this); return; } //[1] System.out.println("Thread #" + Thread.currentThread().getName() + " Start waiting"); Thread.sleep(15000); System.out.println("Thread #" + Thread.currentThread().getName() + " Finish waiting"); System.out.println(); exchange.getResponseHeaders().put(Headers.CONTENT_TYPE, "text/plain"); exchange.getResponseSender().send("Hello world from thread " + Thread.currentThread().getId()); //[2] } }).build(); server.start(); } } When I start it and make three http get request simultaneously I can see this output in console : Thread #XNIO-1 I/O-1 is I/O : handle this Thread #XNIO-1 task-1 Start waiting Thread #XNIO-1 task-1 Finish waiting Thread #XNIO-1 I/O-1 is I/O : handle this Thread #XNIO-1 task-2 Start waiting Thread #XNIO-1 task-2 Finish waiting Thread #XNIO-1 I/O-1 is I/O : handle this Thread #XNIO-1 task-3 Start waiting Thread #XNIO-1 task-3 Finish waiting I think that code beetween //[1] and //[2] should perform in separate thread (and as we can see from the console it really does), but why the main I/O thread are waiting and does not handle other requests? So if my code is correct than it means that Undertow could handle one request in time... What I do wrong? Best, Mikhail