Florencia,
Start by reading this blog post.
Are you using Echoprint or ENMFP? (Did you build codegen from the source at http://echoprint.me or download it from http://static.echonest.com/ENMFP_codegen.zip ? )
It sounds like you might be using ENMFP but feeding it a streamed/recorded file (filestream15.mp3). This is not likely to work. If you post a link to the audio and the json string you get that might help tell what the problem is.
David
