in cocoa,Aout serial communiction using nsfilehandle issues

i have a software about serial communication , it to be develop in MAC os=10.5.8 using cocoa 's nsfilehandle , test ok ,

but when MAC os upgrading to 10.6 ,the program work no开发者_StackOverflow中文版 normal, can't receive nsfilehandle's notification .

it's why ,

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The most likely answer is that something in your program was relying on undefined behavior, and that behavior changed in 10.6.

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i use NSFilehandle to serial communication , dely on the nsfilehandle notification to interact with UI , it run ok On Mac os 10.5.8 ,but upgade to 10.6 , i can't receive any nsfilehandle notification , i using the cocoa normal type ,why have the condition .