Why NetLibSocketOptionSet return errorno--netErrSocketNotConnected

[zhaoweillhch]

I test netsocet app in simulator 5.4(Garnet). I want to apply socket notice 
.But when i use 
NetLibSocketOptionSet(AppNetRefnum,fd,netSocketOptLevelSocket,
                      netSocketOptSockNotice,&option,sizeof
                      (option),AppNetTimeout,&errno)
reuturn errno-netErrSocketNotConnected

what can i do and test ?
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