Let's say you have a virtual machine with two network adapters, both set on 'HostOnly'.
I used to do that and set the first one of those to a fixed IP address, say 10.0.0.1. To this one I coupled the hostname, for instance darlin-vce-db, using the /etc/hosts file. That way I had a fixed, always existing network address for the database.

Together with the database, you install WebLogic, for instance to serve SOASuite, or OSB, or whatever custom application you want to serve. Now, wouldn't it be nice to be able to use WebLogic from a browser out of the virtual machine? Of course, because this is what you do nowadays: almost everywhere I come, servers are hosted on virtualized computing environments, like VMWare VSE or Oracle VM. So that's where the second adapter comes in, dynamically coupled to an address in the form of 192.168.56.101, for instance. Externally, using the etc/host file on your host OS (in my case Windows), you couple that address also to darlin-vce-db.

So you have two /etc/hosts settings for the hostname, darlin-vce-db:
In internally in the VM:

10.0.0.1        darlin-vce-db     darlin-vce-db.darwin-it.local

And externally on your host OS:

192.168.56.101  darlin-vce-db     darlin-vce-db.darwin-it.local

Nothing special, right? Well, WebLogic 11g, apparently just listens to the hostname 'darlin-vce-db', if that is entered as a listen-address. It seems not to care if the request for 'darlin-vce-db' comes from 192.168.56.101 in stead of the 10.0.0.1 to where the hostname actually is bound.

However, in this particular case WebLogic 12c seems to behave differently. If you provice 'darlin-vce-db' as listen address, that is bound to a network adapter that has 10.0.0.1 it expects that requests also come in via that network adapter. It seems to ignore requests that come in via other adapters (in my case 192.168.56.101).

You can solve this partially using Channels: in the Weblogic Console, navigate to the particular managed server, click Protocols, Channels.
Create a new channel:

Give it a name like 'Extern-Intern' or something else properly denoting the purpose of it and choose 'http' as a protocol:

Then Provide the internal address, for instance 'darlin-vce-db', and the external listen address:

Leave the ports to the default listen-port, in this case. Then finish the wizard.
Although this helps in connecting to the WebLogic console, EM, or with the same method on the SOA Server, to the SOA Composer (soaserver:port/soa/composer), BPM Workspace (soaserver:port/bpm/composer) etc., this will not work for JDeveloper.

When trying to deploy a soa composite from JDeveloper, you define/choose a ApplicationServer with connection to the AdminServer. But in case of deploying a composite, the AdminServer figures out which running SOA Servers there are, and let JDeveloper provide the composite to those servers. But then the soaserver(s) refuse(s) the connections from JDeveloper. Testing the ApplicationServer connection will show success for the Http connection to the AdminServer, but fails for all the other components.

The solution is then to denote a particular Network Adapter/ip address and make sure that internally and externally the particular hostname is coupled to that same particular ip-address.