Datasheet

XMPP Stanzas

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data. In all these cases, the client uses the id attribute of the reply stanza to identify which request

stanza it is associated with. In cases where many stanzas of the same type are sent in a short time

frame, this capability is essential because the replies may be delivered out of order.

Presence Stanzas

The <presence> stanza controls and reports the availability of an entity. This availability can range

from simple online and ofﬂine to the more complex away and do not disturb. In addition,

stanzas are used to establish and terminate presence subscriptions to other entities.

In traditional instant messaging systems, presence notiﬁcations are the main source of trafﬁc. To

enable instant communication, it is necessary to know when the other party is available to communi-

cate. When you send an e-mail, you have no idea if the recipient is currently checking and responding

to e-mail, but with instant messages and presence notiﬁcations, you know before the message is sent

if the recipient is around.

For applications in other domains, presence notiﬁcations can be used to signal similar kinds of infor-

mation. For example, some developers have written bots that set their presence to do not disturb

when they are too busy to accept more work. The basic online and ofﬂine states can let applications

know whether a service is currently functioning or down for maintenance.

Normal Presence Stanzas

A normal <presence> stanza contains no type attribute or a type attribute that has the value

unavailable or error. These stanzas set or indicate an entity’s presence or availability for

communication.

There is no

available value for the type attribute because this is indicated instead by the lack of a

type attribute.

Users manipulate their own presence status by sending

<presence> stanzas without a to attribute,

addressing the server directly. You’ve seen two short examples of this already, and these are included

along with some longer examples here:

</presence>

<status>touring the countryside</status>

</presence>

</presence>

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