Good question. You will find that the Coversant XMPP communicator does not send a <presence type="unavailable"/> stanza when it logs out. From what I can tell is that most servers will do that on behalf of the client: it caused me a few minutes of debugging :).
If you want to tell when the client disconnects unexpectedly from another client (e.g. if you have a contact that represents your server availability or something) you could do something like: <presence type="available"> ... <!-- NB: No 'graceful' element --> </presence> <presence type="unavailable"> ... <graceful xmlns="http://www.tempuri.org/xmpp.org/graceful";> </presence> If you receive a stanza without the graceful element you can be sure that the client quit unexpectedly (server sent 'unavailable' on behalf of the client). This raises another important question: most servers AND clients are not XMPP compliant. It is very strange and annoying. Should I take a 'tough luck, you should behave properly' approach to non-compliant clients and servers? > -----Original Message----- > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of > JabberForum > Sent: 02 June 2008 10:25 AM > To: jdev@jabber.org > Subject: [jdev] How is a client crash communicated to the XMPP server? > > > 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 > > > -- > santhosh.kulandaiyan > ------------------------------------------------------------------------ > santhosh.kulandaiyan's Profile: > http://www.jabberforum.org/member.php?userid=16912 > View this thread: http://www.jabberforum.org/showthread.php?t=200 > > _______________________________________________ > JDev mailing list > FAQ: http://www.jabber.org/discussion-lists/jdev-faq > Forum: http://www.jabberforum.org/forumdisplay.php?f=20 > Info: http://mail.jabber.org/mailman/listinfo/jdev > Unsubscribe: [EMAIL PROTECTED] > _______________________________________________ _______________________________________________ JDev mailing list FAQ: http://www.jabber.org/discussion-lists/jdev-faq Forum: http://www.jabberforum.org/forumdisplay.php?f=20 Info: http://mail.jabber.org/mailman/listinfo/jdev Unsubscribe: [EMAIL PROTECTED] _______________________________________________
