ViewExpiredException when submitting JSF form to different host - jsf-2

Question

I want to create login functionality for Admin so that admin can login (from Admin-portal) as any user (in User-portal). (These are two different portal running in two different host).
In Admin-portal, I have have written
<p:dialog>
<form action="http://user-portal.com/index.jsf" method="post"
target="_blank">
<h:inputHidden id="adminId" value="#{userListBean.openAdminId}"></h:inputHidden>
<h:inputHidden id="clientId" value="#{userListBean.openClientId}"></h:inputHidden>
<!-- some other security parameters -->
<input type="submit" value="login"></input>
</form>
</p:dialog>
Problem is in User-portal.
index.jsf
<h:body>
#{customLogin}
</h:body>
CustomLogin bean
#Named("customLogin")
#SessionScoped
public class CustomLogin implements Serializable {
.
.
#PostConstruct
public void customLoginPage() {
HttpServletRequest request = (HttpServletRequest) FacesContext.getCurrentInstance()
.getExternalContext().getRequest();
Map<String, String[]> requestParaMap = request.getParameterMap();
// some admin and user validation and setting other injected bean property base on it
HttpServletResponse response = (HttpServletResponse) FacesContext.getCurrentInstance()
.getExternalContext().getResponse();
string serverName = request.getServerName();
response.sendRedirect(serverName+ "/home.jsf");
// also tried this
// facesContext.getExternalContext().redirect("/home.jsf");
return;
}
CustomLogin bean is session scoped and method "customLoginPage" is invoked postconstruct. So it is running in "RESTORE_VIEW" phase of JSF Lifecycle.
I am getting following error :
javax.faces.application.ViewExpiredException: viewId:/index.jsf - View /index.jsf could not be restored.
at com.sun.faces.lifecycle.RestoreViewPhase.execute(RestoreViewPhase.java:205) [jsf-impl-2.1.28.redhat-3.jar:2.1.28.redhat-3]
at com.sun.faces.lifecycle.Phase.doPhase(Phase.java:101) [jsf-impl-2.1.28.redhat-3.jar:2.1.28.redhat-3]
at com.sun.faces.lifecycle.RestoreViewPhase.doPhase(RestoreViewPhase.java:116) [jsf-impl-2.1.28.redhat-3.jar:2.1.28.redhat-3]
at com.sun.faces.lifecycle.LifecycleImpl.execute(LifecycleImpl.java:118) [jsf-impl-2.1.28.redhat-3.jar:2.1.28.redhat-3]
at javax.faces.webapp.FacesServlet.service(FacesServlet.java:593) [jboss-jsf-api_2.1_spec-2.1.28.Final-redhat-1.jar:2.1.28.Final-redhat-1]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:295) [jbossweb-7.4.8.Final-redhat-4.jar:7.4.8.Final-redhat-4]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:214) [jbossweb-7.4.8.Final-redhat-4.jar:7.4.8.Final-redhat-4]
.
.
.
12:21:24,683 ERROR [org.apache.catalina.core.ContainerBase.[jboss.web].[default-host].[/].[Faces Servlet]] (http-localhost/127.0.0.1:8080-1) JBWEB000236: Servlet.service() for servlet Faces Servlet threw exception: java.lang.IllegalStateException
at org.apache.catalina.connector.ResponseFacade.sendRedirect(ResponseFacade.java:420) [jbossweb-7.4.8.Final-redhat-4.jar:7.4.8.Final-redhat-4]
at com.sun.faces.context.ExternalContextImpl.redirect(ExternalContextImpl.java:602) [jsf-impl-2.1.28.redhat-3.jar:2.1.28.redhat-3]
at javax.faces.context.ExternalContextWrapper.redirect(ExternalContextWrapper.java:462) [jboss-jsf-api_2.1_spec-2.1.28.Final-redhat-1.jar:2.1.28.Final-redhat-1]
Few web.xml content that may be helpful
<context-param>
<param-name>javax.faces.STATE_SAVING_METHOD</param-name>
<param-value>server</param-value>
</context-param>
<context-param>
<param-name>javax.faces.PARTIAL_STATE_SAVING</param-name>
<param-value>false</param-value>
</context-param>
<context-param>
<param-name>javax.faces.RESOURCE_EXCLUDES</param-name>
<param-value>.xhtml .class .properties .xml</param-value>
</context-param>
<context-param>
<param-name>facelets.DEVELOPMENT</param-name>
<param-value>true</param-value>
</context-param>
<servlet>
<servlet-name>Faces Servlet</servlet-name>
<servlet-class>javax.faces.webapp.FacesServlet</servlet-class>
<load-on-startup>1</load-on-startup>
</servlet>
<servlet-mapping>
<servlet-name>Faces Servlet</servlet-name>
<url-pattern>*.jsf</url-pattern>
</servlet-mapping>
I have read ViewExpiredException by BalusC. But here every request to user-portal is fresh. Plus when I change javax.faces.STATE_SAVING_METHOD to client, I am getting "GZIP exception".