Accessing StateData with User/Server/Resource

What StateData do you refer to exactly? I guess you are interested in the one implemented in ejabberd_c2s.erl:

-record(state, {socket,
		sockmod,
		socket_monitor,
		streamid,
		sasl_state,
		access,
		shaper,
		zlib = false,
		tls = false,
		tls_required = false,
		tls_enabled = false,
		tls_options = [],
		authenticated = false,
		jid,
		user = "", server = ?MYNAME, resource = "",
		sid,
		pres_t = ?SETS:new(),
		pres_f = ?SETS:new(),
		pres_a = ?SETS:new(),
		pres_i = ?SETS:new(),
		pres_last, pres_pri,
		pres_timestamp,
		pres_invis = false,
		privacy_list = none,
		ip,
		lang}).

What information are you interested in, IP address, method of connection...?

If I'm understanding you correctly, this is almost the same thing that I needed while hacking my PEP patch. Thus I added ejabberd_sm:get_session_pid/3, which returns the PID of the ejabberd_c2s process, and then ejabberd_c2s:get_subscribed_and_online/1, which returns the data that I need. These functions may or may not eventually find their way into ejabberd proper in this shape, but I hope the code might serve as inspiration…