ICQ is outdated, and few people still use IRC. Use Jabber/XMPP instead.
ejabberd is a great server daemon, conversations is a pretty good client for mobile phones, and pidgin and gajim are usable desktop clients.
Edit:
Some people here are going to suggest using something base on the Matrix protocol, which is pretty nice, but also is rather new, and I'd still use XMPP for anything critical...
ICQ is outdated, and few people still use IRC. Use Jabber/XMPP instead.
ejabberd is a great server daemon, conversations is a pretty good client for mobile phones, and pidgin and gajim are usable desktop clients.
Edit:
Some people here are going to suggest using something base on the Matrix protocol, which is pretty nice, but also is rather new, and I'd still use XMPP for anything critical...
(post is archived)