how to play live network stream

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Hi. How to play a live network stream by opencv in Windows7?
I spent a lot of time, read forums and documentation, tried everything (udp, multicast udp, rtp, even named pipe), but nothing works.

VideoCapture cap; cap.open("udp://:1234); //does not work
cap.open("udp://234.1.2.3:1234); //does not work
cap.open("rtp://:1234); //does not work
cap.open("rtp://@:1234); //does not work
cap.open("rtp://234.1.2.3:1234); //does not work
cap.open("rtp://@234.1.2.3:1234); //does not work
cap.open("\.\pipe\MyPipe); //does not work

Thanks