socket program works fine on windows phone emulator but does not work on device

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C#

Windows

phone

i have developed a socket program, which works fine on windows phone emulator but does not when i deploy the app on windows phone device.
my program is perfect but i do not know why it is not working on device.i have also tried to run a code of "tic-tac-toe over socket sample" from microsoft developer network/samples but the problem remains same, it works on emulator but does not work on device.
i am wondering to find the solution. Thank You