Oracle 12c Release 2 Database Configuration Assistant installation on CentOS - The port is already in use
Oracle support doc [DBT-06103] The port (5,500) is already in use. ACTION: Specify a free port (Doc ID 2277154.1) says to put the unqualified hostname into /etc/hosts too. i.e:

192.168.10.113 CentOS-Dev-db-12c.Company.local CentOS-Dev-db-12c