Ejabberd is a Jabber/XMPP + MQTT + SIP server written in Erlang, featuring: * distributed operation with load-balancing across a cluster; * fault-tolerant database replication and storage on multiple nodes, allowing nodes to be added or replaced "on the fly"; * virtual hosting (several virtual domains can be served using a single ejabberd instance); * XMPP compliance; * MQTT 5 compliance; * SIP service; * web-based administration; * SSL/TLS support; * conferencing via Multi-User Chat; * Jabber Users Directory, based on users' vCards; * service discovery; * shared roster.