How to make Xdebug work on Centos and Zend Studio?

Question

I have two virtual machines: a Debian VM with Nginx and PHP-FPM and a Centos VM with Apache. On the Debian VM Xdebug works. On the Centos one it doesn't. When I start a debug session in my IDE (eclipse based Zend Studio 12.5), the lauchiung progress stopps at 78%:

The main Xdebug configs seem to be set correctly. At least they work for my Debian VM:

; Enable xdebug extension module
zend_extension=/usr/lib64/php/modules/xdebug.so

; remote
xdebug.remote_enable=1
xdebug.remote_autostart=1
xdebug.remote_host="192.168.178.34"
xdebug.remote_connect_back=1
xdebug.remote_port=9000
xdebug.remote_handler=dbgp
xdebug.remote_log="/var/log/xdebug_remote.log"

xdebug.idekey="ECLIPSE_DBGP"

; profiler
xdebug.profiler_enable=0
xdebug.profiler_enable_trigger=0
xdebug.profiler_output_dir="/tmp"

What can be the problem here and how to get Xdebug working?

---

Current settings:

Answer 1

A look into the log has helped:

I: Checking remote connect back address.
I: Remote address found, connecting to 192.168.56.1:9000.
E: Time-out connecting to client. :-(
Log closed at 2015-05-11 12:06:29

And then I read here:

xdebug.remote_connect_back [...] setting should not be defined and enabled. When it is enabled, it completely ignores the former setting [...]

I set xdebug.remote_connect_back to 0. Now Xdebug is working.