INFO 2018-08-15 00:12:47,330 hostname.py:67 - agent:hostname_script configuration not defined thus read hostname 'test-new-server-6' using socket.getfqdn().
INFO 2018-08-15 00:12:47,557 PingPortListener.py:50 - Ping port listener started on port: 8670
INFO 2018-08-15 00:12:47,560 main.py:437 - Connecting to Ambari server at https://test-new-server-6:8440 (12.12.12.11)
INFO 2018-08-15 00:12:47,560 NetUtil.py:70 - Connecting to https://test-new-server-6:8440/ca
ERROR 2018-08-15 00:12:47,609 NetUtil.py:96 - [Errno 8] _ssl.c:492: EOF occurred in violation of protocol
ERROR 2018-08-15 00:12:47,609 NetUtil.py:97 - SSLError: Failed to connect. Please check openssl library versions. 
Refer to: https://bugzilla.redhat.com/show_bug.cgi?id=1022468 for more details.
WARNING 2018-08-15 00:12:47,609 NetUtil.py:124 - Server at https://test-new-server-6:8440 is not reachable, sleeping for 10 seconds...
", None)

Connection to test-new-server-6 closed.
SSH command execution finished
host=test-new-server-6, exitcode=0
Command end time 2018-08-15 00:12:49

Registering with the server...
Registration with the server failed.   

# Solution For CentOS 7, Debian 7, Ubuntu 14 & 16, or SLES 12 (Python 2.7)
By adding below config in [security] section of

vim /etc/ambari-agent/conf/ambari-agent.ini
force_https_protocol=PROTOCOL_TLSv1_2


vim /etc/python/cert-verification.cfg 
[https] 
verify=disable

# Solution for CentOS 6, or SLES 11 (Python 2.6)
# Locate the jdk.tls.disabledAlgorithms property and remove the 3DES_EDE_CBC reference
# Save the file, and restart the Ambari Server
vim /usr/java/jdk1.8.0_171-amd64/jre/lib/security/java.security