when visit /sap/bc/soap/rfc, 500 error returned

hi

I program a webservices demo by webdynpro. I create that demo to call a abap webservices.

But when i run the webdynpro program. An exception throws Service call exception; nested exception is: java.lang.NullPointerException.

I read the wsdl file generated by R/3. I try to visit "http://<site>:<port>/sap/bc/soap/rfc" in the browser. 500 error returns with no information.

Can i directly visit that URL? I think it will return a soap response page. What's wrong?

thanX

elliot