Hi Walid,
If your Mango is running op port 8080 (you access it on your localhost with http://localhost:8080), then you could configure your router under NAT/portforwarding/application_sharing (depends on your router) like this: set it to forward public TCP port 8080 of your router (or perhaps 80 if you like) to the LAN IP address and TCP port 8080 of the machine on your LAN (for example 192.168.0.1).
Perhaps stating the obvious, but ofcourse you should use a static LAN address for you server as well, or alternatively configure your router to always assign the same IP address to the paricular ethernet MAC address of your server.