IceCast is an open source media streaming server. It is still being developed and updated. Most IceCast servers run on Port 8000 but with different "mounting points" (/station /live.mp3 /live.aac etc)
Each stream is on a different port. You can stream in MP3, AAC and OGG.
The original version of Shoutcast works well but has not been updated in many years and uses HTTP0.9 which is not now supported by a number of browsers. It will, however, still work with apps.
The later version also has not been updated for sometime. But it needs a HASH code for your station to operate fully. If you move servers, you will have to get your HASH code updated. This version can run several streams for the same station on the same port but with different StreamID's
There are 3 main encoding formats for streams.
Widely used and playable by all browsers and mobile phones.
Better quality than MP3 at lower bit rates, but some browsers may have problems playing and older mobile phones.
Less widely used than the other two methods, but again better quality than MP3.