smartclient server separate host from smartclient client html/js

Looking at a possible 3 host setup:

host 1. Apache webserver for html and the client side isomorphic js libraries, skins etc.

host 2. Tomcat server for the smartclient server side java stuff

host 3. MySQL server to persist the data.

Question: How to I pass the address of host 2 to the clients so that they can talk to the server side java. The examples all seem to assume that the client side html and the server java live on one host under one webroot.

I'm suspect I'm missing a simple config item somewhere.

Thanks
Russ Poyner