Chloe is a free and simple realtime web server that doesn't suck; or at least won't suck when it's finished.
When you have data that you want to send back to the browser, send a POST to Chloe, which will relay it back to the connected browser .
Detailed instructions on how to install and use the Chloe utility on your Mac are available HERE.
Chloe is cross-platform and it works on Mac OS X, Windows and Linux. Binaries for the Windows and Linux platforms are available on the project's homepage.