Vaadin + Google App Engine - communication problem

I’m developing RESTful web-service with Vaadin and I want to host it on Google App Engine, but after deployment I faced strange problem: after any action I receive “Communication problem”

Steps to reproduce:

  1. Go to

  2. Enter any text to text area and press “Process” button.

My web.xml:

<?xml version="1.0" encoding="UTF-8"?> Vaadin Web Application Vaadin production mode productionMode false heartbeatInterval 300 60 Vaadin Application Servlet com.vaadin.server.VaadinServlet Vaadin application class to start UI Vaadin Application Servlet /*

My appengine-web.xml:

<?xml version="1.0" encoding="utf-8"?> checkstyle-ast-viewer 1 true true
    <property name="java.util.logging.config.file" value="WEB-INF/"/>