java:/ namespace is only accessible from within the same JVM
So what should I do ?
If you have to use a datasource from your client I guess most J2EE programmers would agree that you have a problem with the design of your application.
Use the datasource in a session bean and do remote calls from the client.
The whole idea behind J2EE is to keep the bussiness logic on the server (including database access) and keep the client as thin as possible.