Error condition on socket for SYNC: Connection refused，表示redis主服务器拒绝redis从服务器的连接。这样从官方默认的配置文档redis.conf中说起。

redis.conf 中 【bind】配置的用法：（一句话:bind配置了什么ip，别人就得访问bind里面配置的ip才访问到redis服务。）

# By default, if no "bind" configuration directive is specified, Redis listens
# for connections from all the network interfaces available on the server.
# It is possible to listen to just one or multiple selected interfaces using
# the "bind" configuration directive, followed by one or more IP addresses.
#
# Examples:
#
# bind 192.168.1.100 10.0.0.1
# bind 127.0.0.1 ::1
#
# ~~~ WARNING ~~~ If the computer running Redis is directly exposed to the
# internet, binding to all the interfaces is dangerous and will expose the
# instance to everybody on the internet. So by default we uncomment the
# following bind directive, that will force Redis to listen only into
# the IPv4 lookback interface address (this