Discovery

As with all other parts of XMPP, if we want to discover and find information about a pubsub provider, we use our old friend (by now, right?) DISCO. Pubsub systems will often sit on their own domain under an XMPP server domain (often running as a component; more on that in the next chapter).

To discover a pubsub system, Marty would run a DISCO#items query against the parent domain and see what was available:

<iq type='get' id='query1' 
from='[e-mail]/street' 
to='hill.valley'> 
  <query xmlns='http://jabber.org/protocol/disco#items'/> 
</iq> 

The server then responds with a set of items that it's hosting:

<iq type='result' id='query1' 
from='hill.valley' 
to='[e-mail]/street'> 
  <query xmlns='http://jabber.org/protocol/disco#items> 
    <item jid='pubsub.hill.valley'/> 
    <item jid='chat.hill.valley'/> 
    <item jid='identity.hill.valley'/> 
  </query&gt...