I would imagine it's a relay configuration. When we did shoutcasting we used to run winamp with the shoutcast plugin and the shoutcast server on the same machine. You don't have to do this but we were already in a building with 3x155 meg connectivity to jaNET. I could quite easily have run the encoder at home on my adsl which would have sent one stream out to the server at uni. That machine then accepted listeners and streamed from there. Very simple.