Extensible Messaging and Presence Protocol (XMPP)

Extensible Messaging and Presence Protocol (XMPP) is a communications protocol for message-oriented middleware based on XML (Extensible Markup Language).[1] The protocol was originally named Jabber,[2] and was developed by the Jabber open-source community in 1999 for near real-time, instant messaging (IM), presence information, and contact list maintenance. Designed to be extensible, the protocol has also been used for publish-subscribe systems, signalling for VoIP, video, file transfer, gaming, Internet of Things (IoT) applications such as the smart grid, and social networking services.

The XMPP network uses a client–server architecture; clients do not talk directly to one another. The model is decentralized, anyone can run a server, but neither anonymous nor peer to peer, like Skype. By design, there is no central authoritative server as there is with services such as AOL Instant Messenger or Windows Live Messenger.

Every user on the network has a unique Jabber ID, often abbreviated as JID. To avoid requiring a central server to maintain a list of IDs, the JID is structured like an email address with a username and a domain name (or IP address) for the server where that user resides, separated by an at sign (@), such as username@example.com.