Error:
java.io.FileNotFoundException: Response: '500: Internal Server Error' for url:
'http://www.xxxx.com//myServlet/anyfile.exml'
at weblogic.net.http.HttpURLConnection.getInputStream (HttpURLConnection.java:380)

The URL is correct.
When it fails, on IE browser, receive the following message,

The RPC server is unavailable
The remote procedure call failed.

Servlet receives xml and set it into session.
This class set or get session.
Servlet is called many times.

Using weblogic 8.1