>Next, the XML data file needs to be sent ("forwarded") to another client computer on this WAN. My client-side application watches for incoming XML files and updates its' free tables when XML files are found in a specific directory.

If your solution is thus far file based, and the client machines are on the same network, then the simplest solution would be to allow the server to access drives on the client via UNC, and just copy the file:

COPY FILE "c:\myxml.xml" TO "\\Client1\SomeShare\SomeFolder\myxml.xml"