def expect(self, expectedLen, callback = None):
        """
        @summary:  Set next automata callback, 
                    But this callback will be only called when
                    data have expectedLen
        @param expectedLen: in bytes length use to call next state
        @param callback: callback call when expected length bytes is received
        """
        self._expectedLen = expectedLen
        #default callback is recv from LayerAutomata
        self.setNextState(callback)
def expect ( self , expectedLen , callback = None ) : self . _expectedLen = expectedLen self . setNextState ( callback )
@summary:  Set next automata callback, 
                    But this callback will be only called when
                    data have expectedLen
        @param expectedLen: in bytes length use to call next state
        @param callback: callback call when expected length bytes is received