Object #<Server> has no method 'configure'

http://stackoverflow.com/questions/8584442/configuring-nginx-and-socket-io

io.configure(function() {
        io.enable('browser client etag');
        io.set('transports', [
         'websocket','xhr-polling'
  ]);
});

提示　Object # has no method 'configure' 怎么样设置socket.io的参数呢？