[Leace]

ejabberd [0], XMPP server is written in erlang and powers chat in some of the biggest MMORPGs [1].

[0]: https://github.com/processone/ejabberd

[1]: https://xmpp.org/uses/gaming.html

[77pt77]

By used in MMORPGs you mean the chatting component, not the actual game-play network protocol.

[yawaramin]

That's exactly what they said.