Want to broadcast your own radioshow? search duckduckgo:
Nicecast (Mac OS X)
1. Download one of the tools, read the docs for the configuration (or ask for help). Surf to http://localhost:8000 to see if you hear music.
2. Find your modem, log into it (when at home, your modem address probably is http://192.168.1.1 or similar). It's also common for lousy ISP's to to offer access to your modem through an online control panel, probably accessible through something like https://myaccount.internetprovider.com .
3. Find the "Port Forward" settings in the control panel of your modem, and add your computer (the box where you installed icecast) so it's port 8000 is reachable from the interwebz.