You sure you've followed the instructions above to the letter. Did you save the file as .asf? Make sure sopcast is running on some channel right click the image and click properties to see if you've got the right ip and port.
Hope this helps!
p.s. looks like you may have an extra / at the end of the address "http://127.0.0.1:8902/", try this:
http://127.0.0.1:8902