fixed a linux compatibility issue in the UDP test cases
fixed a linux compatibility issue in the UDP test cases

chucklu/SuperSocket,jmptrader/SuperSocket,fryderykhuang/SuperSocket,ZixiangBoy/SuperSocket,kerryjiang/SuperSocket,mdavid/SuperSocket,fryderykhuang/SuperSocket,jmptrader/SuperSocket,mdavid/SuperSocket,memleaks/SuperSocket,mdavid/SuperSocket,ZixiangBoy/SuperSocket,kerryjiang/SuperSocket,chucklu/SuperSocket,chucklu/SuperSocket,fryderykhuang/SuperSocket,jmptrader/SuperSocket,ZixiangBoy/SuperSocket