Presently I use "iptux" for sending messages and sharing files over my hostel LAN, but the interface isn't quite convenient. Is there a better LAN messaging and file-sharing application on Ubuntu? I don't intend to use "samba" as I need to send messages too. If you need the specifications; Ubuntu 12.10, Unity 6.
Checkout the open source project Openfire, its a jabber protocol server so you will be able to setup your own private network and still use popular applications like Pidgin as it uses the XMPP protocol.
Checkout the plugin page to see how extensible it is and if it meets your needs.
It's java based so install should be a breeze.