Shiro redirect to a other Vaadin application, i get a communication problem

General
1

i have 2 tomcats and i want from one tomcat to other a redirect with Shiro. In both tomcat running a vaadin application.

When i use WebUtils.issueRedirect() from Shiro, i get a error that
Communication Problem Invalid Status Code 0 (Server down?)

But with
getUI().getPage().open()
 it works.

I need help!!