Hi,

>I would like to check what is the public IP of my network.

The easiest way would be if you have access to an external web server. The web server reports the current IP address in one of the server variables. A web application could do nothing but report your IP address. With AFP 3.0 this would look like this:

<%
? Request.ServerVariables("REMOTE_ADDR")
%>

Many web pages on the web already display the IP address. A quick search on google brought up one example: http://ci.phaseburn.net. Aside from HTTP, you can use any kind of server you want. No matter which one you use, the only way to get the IP address behind a Router is to send a request to the outside and the let the outside party take note of the IP address.