Clone Open Fire Server

I need a program for the below spec. Please clone the below link as much as possible. [login to view URL] Openfire but i should be able to write plugins and expand the server on my own. It should also be highly scalable as we really do not know what the impact will be when we launch but its should roughly be able to handle 50 000 concurrent connections on one server if possible. There will be no need for the things like authentication, chat ect.. just the simple server with support for plugins like openfired. Thank you