Hi,
In the EMS installation folder, there’s a "demo" subdirectory which contains a demonstration "emsdemo.html" showing how to access the EMS API thru the HTTP interface. Basically it encodes your parameters in base64 before appending them to your HTTP request.
For more details, please refer to page 4 of the following document:
http://www.evostream.com/evo_evals/EMS%20How%20Tos.pdf
Cheers,
Don