Prosody is a relatively simple and light-weight XMPP chat server written in Lua. It’s a good choice for an easy private chat server.
# apt-get install prosody
$ cat /etc/prosody/README
Prosody configuration directory
===============================
The configuration file /etc/prosody/prosody.cfg.lua should contain
only global settings.
Per-host configuration files should be placed in /etc/prosody/conf.avail/,
and the active ones should be linked in /etc/prosody/conf.d/
The config files are well commented.
The default prosody.cfg.lua file has sane defaults.
# cp /etc/prosody/conf.avail/example.com.cfg.lua /etc/prosody/conf.avail/host.example.com.cfg.lua
# ln -s /etc/prosody/conf.avail/host.example.com.cfg.lua /etc/prosody/conf.d/host.example.com.cfg.lua
Open port 5222:
# iptables -A INPUT -p tcp -m tcp --dport 5222 -j ACCEPT -m comment --comment "Server XMPP (prosody)."