IO Error: The Network Adapter could not establish the connection

Network Adapter could not establish the connection

Error: While trying to connect to database from SQL* PLUS 

             Status: Failure - Test Failed: IO Error: The Network Adapter could not establish the connection

Solution:

                1. Check the host, SID and port entry in Listener.ora file

                2. Stop the firewall

Stop the Firewall: 

[oracle@test test_test]$ systemctl stop firewalld

==== AUTHENTICATING FOR org.freedesktop.systemd1.manage-units ===

Authentication is required to manage system services or units.

Authenticating as: root

Password:

==== AUTHENTICATION COMPLETE ===

[oracle@testr12 testr12_test]$ systemctl disable firewalld

==== AUTHENTICATING FOR org.freedesktop.systemd1.manage-unit-files ===

Authentication is required to manage system service or unit files.

Authenticating as: root

Password:

==== AUTHENTICATION COMPLETE ===

Removed symlink /etc/systemd/system/basic.target.wants/firewalld.service.

Removed symlink /etc/systemd/system/dbus-org.fedoraproject.FirewallD1.service.

==== AUTHENTICATING FOR org.freedesktop.systemd1.reload-daemon ===

Authentication is required to reload the systemd state.

Authenticating as: root

Password:

==== AUTHENTICATION COMPLETE ===

[oracle@test test_test]$