As I figured out, Comet Servlet 3 Push cannot be used with ZK 6.5.1.1 EE OSGi and GlassFish 3.1.2. Class org.zkoss.web.servlet.Servlets checks if interface javax.servlet.annotation.WebServlet can be found on classpath, but bundle zweb does not import package javax.servlet.annotation. Hence Servlets.isServlet3() will never return true and org.zkoss.zkmax.ui.comet.CometServerPush.defaultAsync() will always return false.

Adding javax.servlet.annotation to org.osgi.framework.bootdelgation does not work under GlassFish 3.1.2, so the only chance to use Comet Servlet 3 Push is to import javax.servlet.annotation in zweb's MANIFEST file.