[[https://en.wikipedia.org/wiki/XMPP | Extensible Messaging and Presence Protocol (XMPP)]] is a communication protocol for message-oriented middleware based on XML (Extensible Markup Language)
XMPP has several features used by the 0 A. D. [[lobby]] and more features are planned leveraging XMPP's various extensions known as [[ https://xmpp.org/extensions/ | XEPs]]
XEP-0045 Multi-User Chat
XEP-0166 Jingle
XEP-0176 Jingle ICE-UDP Transport Method
planned:
XEP-0060 Publish-Subscribe (aka pubsub)