View the source of this page for details on how it was called. If you compile mozilla DEBUG, the message sent and received will be logged to the console.
This works by calling a SOAP service listed on X Methods Website using the low-level SOAP API in Mozilla.
Since this service is not friendly to untrusted applets, it may not be called without requesting additional privileges from the user. It can be made friendly by accepting the verifySource header or by loading the page and proxy from the domain of the service.
Experimenters may wish to add other tests which exercize services, with specific user interfaces such as the one in this test.