Openfire is a XMPP (Jabber) server written in Java. It has facility for developers to create plugins that can extend the server's functionality.
Openfire is a real time collaboration (RTC) server licensed under the Open Source GPL. It uses the only widely adopted open protocol for instant messaging, XMPP (also called Jabber). Openfire was once known as Wildfire and includes a number of plugins that integrate with other communications platforms, including commercial offerings from Jive Software