DevOps, CI/CD and Automation

As I wrote in a different post in this forums, I've got a problem
when I try to connect to a XE Database Server.

Using the local Apache/PHP5 installation on this machine was no problem.
I could connect and fetch data from the Server with the following DSN:
$dsn = "oci8://username:password@/localhost/XE";

But when I tried to connect to this Server from a different machine inside my LAN and substituted the "localhost" part of the DSN with the IP adress of the Server to sth. like :
$dsn = "oci8://username:password@/192.168.178.30/XE";

I always get the following connection error from the MDB2 package:
<< MDB2 Error: connect failed - _doConnect: [Error message: unable to establish a connection] >>

Some words on the system setup of my client machine:
On my client machine I've installed the "Oracle Client 10g Express Edition" through the Windows installer.
I also downloaded the "instantclient-basic-win32-10.2.0.3-20061115.zip" and unzipped it into my Apache/PHP5 enviromnent to make the *.dll's accessible for the webserver on my client.
After each installation step I rebooted the whole client machine to check if sth. changed, but nothing seemed to work/change/improve anything.
I also tried to connect through the SQL prompt of the Oracle Windows client.
It just tells me (on my German version) that the connect command was applied (durchgeführt). My problem is that I don't really know anything about the whole SQL Plus thing, so that I could execute a SELECT statement to check if the connect was truely successfull. Probably a tip on how to execute a basic statment in SQL Plus or a link to a manual/documentation would help me out (I couldn't find any download link on the Oracle website...).

Some final thoughts of mine:
* Do I have to change my XE setup to make it accessible for remote (php) clients ?
* Am I missing something totally different ?

Thanks for any help or suggestion.

** Michl