During the DE server installation dialog, in a fresh installed Linux machine, a "The port is currently in use" error message related to Desktop Client port can be displayed, as below:
This can be caused due to a problem in name resolution system of the machine.
Workload Automation DE 11.3.x
Workload Automation DE 12.x
It's necessary to add an entry to etc/hosts file containing the hostname (FQDN and short name) and ip address of the server.