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You send an initial presence stanza to your server: How Presence Is Propagated | 33 Yes, this is the smallest XMPP stanza you will ever see! Initial presence can also include more detailed availability status information, as described next. 3. ] 4. Now, everyone who is subscribed to your presence knows that you are online and available for communication. But how do you know if they are online? ] 5. Once your contacts’ servers receive the probes, they check permissions according to their records.

This value further differentiates how each kind of stanza is processed by the recipient. • The child element(s), which define the payload of the stanza. The payload might be presented to a user or processed in some automated fashion as determined by the specification that defines the namespace of the payload. The following sections provide a brief introduction to these factors, and we will explore them throughout this book as we unfold the meaning of various stanza kinds, type attribute values, and payload definitions.

At its most basic, presence is an on-off indication that an entity is either online or offline. ” These states can be personalized using status messages such as “on a train” or “I’m writing, don’t bother me right now” (a state we have used quite a bit recently). In IM applications of XMPP, presence is typically displayed in your roster, which is a kind of presence-enabled contact list. Your roster contains a list of JabberIDs and the state of your presence subscriptions with those entities.