Error while connecting to agent controller server at /10.180.219.61:16001

[OnTheWay]

[root@LetvWebServer-D44BF0 ngrinder-agent]# cat agent.conf
common.start_mode=agent
agent.controller_host=10.180.219.123
agent.controller_port=16001
agent.region=NONE

but, start agent has problem:

2017-05-27 17:56:22,194 INFO  agent controller daemon  :  The agent controller daemon is started.
2017-05-27 17:56:22,196 ERROR agent controller  :  Error while connecting to agent controller server at /10.180.219.61:16001