ShoutCast2 + sc_trans2 installations use 4 ports, starting at the port number assigned to the stream. So if you assign port 8000 to your stream, the structure will be:
8000 - stream port (used to tune in)
8001 - Shoutcast DNAS v1 source connection port
8002 - ShoutCast DNAS v2 source connection port
8003 - sc_trans v2 administration port