santhosh.kulandaiyan
06-02-2008, 10:25 AM
Hi,
I would like to discuss about what happens when an XMPP client crashes and how this information is communicated to the server..
I have a server S and 2 clients C1 and C2 connected to the server. C1 has C2 in its roster list and C2 has C1 in its roster list.
If C1 gracefully logs out, then an iq stanza of type unavailable is sent to the server and the server broadcasts that stanza to all JIDs which have a subscription of from or both.
However, I have been trying to search for what happens when the client crashes (or exits ungracefully). I havent arrived at the answer yet. Here is what RFC 3291 says :
"5.1.5. Unavailable Presence
Before ending its session with a server, a client SHOULD gracefully become
unavailable by sending a final presence stanza that possesses no 'to'
attribute and that possesses a 'type' attribute whose value is
"unavailable" (optionally, the final presence stanza MAY contain one or
more <status/> elements specifying the reason why the user is no longer
available). However, the user's server MUST NOT depend on receiving final
presence from an available resource, since the resource may become
unavailable unexpectedly or may be timed out by the server. If one of the
user's resources becomes unavailable for any reason (either gracefully or
ungracefully), the user's server MUST broadcast unavailable presence to
all contacts (1) that are in the user's roster with a subscription type of
"from" or "both", (2) to whom the user has not blocked outbound presence,
and (3) from whom the server has not received a presence error during the
user's session; the user's server MUST also send that unavailable presence
stanza to any of the user's other available resources, as well as to any
entities to which the user has sent directed presence during the user's
session for that resource (if the user has not yet sent directed
unavailable presence to that entity). Any presence stanza with no 'type'
attribute and no 'to' attribute that is sent after sending directed
unavailable presence or broadcasted unavailable presence MUST be
broadcasted by the server to all subscribers. "
Do we interpret that as : "the server will 'somehow' know that the client has crashed and then publish the unavailable stanzas to everyone subscribed to that JID ?
Please clarify.. :-)
-santhosh
I would like to discuss about what happens when an XMPP client crashes and how this information is communicated to the server..
I have a server S and 2 clients C1 and C2 connected to the server. C1 has C2 in its roster list and C2 has C1 in its roster list.
If C1 gracefully logs out, then an iq stanza of type unavailable is sent to the server and the server broadcasts that stanza to all JIDs which have a subscription of from or both.
However, I have been trying to search for what happens when the client crashes (or exits ungracefully). I havent arrived at the answer yet. Here is what RFC 3291 says :
"5.1.5. Unavailable Presence
Before ending its session with a server, a client SHOULD gracefully become
unavailable by sending a final presence stanza that possesses no 'to'
attribute and that possesses a 'type' attribute whose value is
"unavailable" (optionally, the final presence stanza MAY contain one or
more <status/> elements specifying the reason why the user is no longer
available). However, the user's server MUST NOT depend on receiving final
presence from an available resource, since the resource may become
unavailable unexpectedly or may be timed out by the server. If one of the
user's resources becomes unavailable for any reason (either gracefully or
ungracefully), the user's server MUST broadcast unavailable presence to
all contacts (1) that are in the user's roster with a subscription type of
"from" or "both", (2) to whom the user has not blocked outbound presence,
and (3) from whom the server has not received a presence error during the
user's session; the user's server MUST also send that unavailable presence
stanza to any of the user's other available resources, as well as to any
entities to which the user has sent directed presence during the user's
session for that resource (if the user has not yet sent directed
unavailable presence to that entity). Any presence stanza with no 'type'
attribute and no 'to' attribute that is sent after sending directed
unavailable presence or broadcasted unavailable presence MUST be
broadcasted by the server to all subscribers. "
Do we interpret that as : "the server will 'somehow' know that the client has crashed and then publish the unavailable stanzas to everyone subscribed to that JID ?
Please clarify.. :-)
-santhosh