J2ME : Communication between a client and a J2EE application server

I am working on a wireless application extension to an existing J2EE application.

I am to come up with a"mobile" edition of a use case.
The target device is a IPAQ running SuperWABA JVM.

It has been decided that XML will be the main form of data transfer between the client and the J2EE application.

The floor plan for communication will be as follows :
1) J2ME client makes httpconnection to a Servlet (new) running alongside the exisitng application
2) Servlet calls pre - existing codes to get/process data
3) Servlet generates xml using the reponse.printwriter()
4) Servlet returns.
5) Client receives XML and parses it using a modified version of nano XML.
6) Client process and intakes User input
7) Client writes User input into XML and transfer to Server
8) Server reads XML and processes the input XML
9) Server returns

My question is : how to accomplish (7)?
I know how to write XML to a local file.. but how do i transfer it over (so that its accessable to the servlet) ?

Thanks