How do I determine if a specific port is open for incoming traffic behind firewall

view story

http://stackoverflow.com – I am trying to stream audio using Android's MediaPlayer library. In some cases, the stream URL is of an unusual port. For example, If I were to try and access this stream from behind a firewall in my browser, it gives me an "Oops! Google Chrome could not connect to" error. Frrom media player in my android device, I get : MusicStream(1806): Media Player Error: Stream URL Invalid (1) -1004 At the moment, I'm just handling this exception. However, I would like to be able to pre-test the URL to determine if the stream is available before starting (HowTos)