Servlets where not designed to make remote calls (from one JVM to an other) by default. This sounds more like a design issue than a servlet issue.
You may want to consider taking the business logic in the servlet to be called and placing it into an
EJB. Both servlets (and any other client down the road) will just call the EJB when that functionality is required.
There really is no way to pass an Object from one servlet to an other, and you probably shouldn't design a system to do so. As stated above, you may look up an other J2EE app and pass the Req/Res to a URL in that app, but as far as passing an Object around, that is what EJBs are for.