node 连接 redis 数据库出错 （发生异常: ReplyError）

Question

var redis = require('redis'),
RDS_PORT = 6379, //端口号
RDS_HOST = '127.0.0.1', //服务器IP
RDS_OPTS = {}, //设置项
client = redis.createClient(RDS_PORT,RDS_HOST,RDS_OPTS);