When "There is a process already using the admin port 4848", but it is not true

When you try to start Payara 5 / GlassFish with:

asadmin start-domain

...and you get the following error:

There is a process already using the admin port 4848 -- it could be another instance of Payara Server or Payara Micro. Command start-domain failed.

although there is no running Java process and the port is not occupied, you hostname is probably not pingable:

ping $(hostname)

output: Request timeout

Solution:

Add the following line to the /etc/hosts file:

127.0.0.1 [YOUR_NOT_PINGABLE_HOSTNAME]