[GeoNetwork-users] Timeout on map.addServices.embedded

Hello folks,
after some time devoted configuring GeoNetwork, I have my site online.
I have got just a strange trouble with WMS source:

I use GeoServer for WMS and it's installed on the same machine of
GeoNetwork; when I add the WMS data source inside the metadata if I use
the ip of the machine (i.e. http://123.123.123.123/geoserver/wms) once I
add it to the viewer, the request goes in timeout with this error:

<error id="error">
<message>Connection timed out</message>
<class>ConnectException</class>
<stack>
<at class="java.net.PlainSocketImpl" file="PlainSocketImpl.java"
line="-2" method="socketConnect"/>
<at class="java.net.PlainSocketImpl" file="PlainSocketImpl.java"
line="333" method="doConnect"/>
<at class="java.net.PlainSocketImpl" file="PlainSocketImpl.java"
line="195" method="connectToAddress"/>
<at class="java.net.PlainSocketImpl" file="PlainSocketImpl.java"
line="182" method="connect"/>
<at class="java.net.SocksSocketImpl" file="SocksSocketImpl.java"
line="366" method="connect"/>
<at class="java.net.Socket" file="Socket.java" line="519"
method="connect"/>
<at class="java.net.Socket" file="Socket.java" line="469"
method="connect"/>
<at class="sun.net.NetworkClient" file="NetworkClient.java" line="163"
method="doConnect"/>
<at class="sun.net.www.http.HttpClient" file="HttpClient.java"
line="394" method="openServer"/>
<at class="sun.net.www.http.HttpClient" file="HttpClient.java"
line="529" method="openServer"/>
</stack>
<request>
<language>it</language>
<service>map.addServices.embedded</service>
</request>
</error>

Using instead http://localhost/geoserver/wms works fine.
In any case I can access Geoserver using GIS Desktop client and all
works fine.

Can be a firewall problem? All other operations (download, add external
WMS, ecc..) are ok.

Thank you for your help
Luca