Session 0x0 for server null, unexpected error, closing socket connection and attempting reconnect

本地tomcat启动连接注册中心，报错信息如下：
2016-11-11 18:27:37,185 INFO  org.apache.zookeeper.ClientCnxn.logStartConnect:966 - Opening socket connection to server localhost/127.0.0.1:2181. Will not attempt to authenticate using SASL (unknown error)
2016-11-11 18:27:37,191 WARN  org.apache.zookeeper.ClientCnxn.run:1089 - Session 0x0 for server null, unexpected error, closing socket connection and attempting reconnect
java.net.ConnectException: Connection refused
at sun.nio.ch.SocketChannelImpl.checkConnect(Native Method)
at sun.nio.ch.SocketChannelImpl.finishConnect(SocketChannelImpl.java:744)
at org.apache.zookeeper.ClientCnxnSocketNIO.doTransport(ClientCnxnSocketNIO.java:350)
at org.apache.zookeeper.ClientCnxn$SendThread.run(ClientCnxn.java:1068)

排查问题 ：
$ ./zkServer.sh status
JMX enabled by default
Using config: /Users/zhangxiaolong/Documents/zhangxiaolong/program/zookeeper-3.4.5/bin/../conf/zoo.cfg
Error contacting service. It is probably not running.
bjjbgi-7-103:bin zhangxiaolong$ 

发现是zk没有启动导致。

重新启动zk即可