Difference between revisions of "XEP-Remarks/XEP-0045: Multi-User Chat"

XEP-Remarks/XEP-0045: Multi-User Chat (view source)

298 bytes added , 22:41, 6 April 2018

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 = Am I still there? =
-Current MUC / server implementations do not send offline-presence packets to participants on service restart. Therefore, a client will think it is still joined to a MUC indefinitely.
+Current MUC / server implementations do not send offline-presence packets to participants on service restart. Therefore, a client will think it is still joined to a MUC indefinitely, only seeing silence.
 There is no portable/reliable mechanism to check if the client is still joined, and no clean way to re-sync the state if it is not joined.
+Sending a "silent" message or presence update to the MUC will lead to O(N²) complexity (if every client does so), killing all our batteries.
-This problem needs to be solved at the MUC service / service-hosting server level eventually, but a workaround is needed on the client side.
+The "most viable" workaround is:
-Maybe a periodic presence packet can be sent to the MUC, checking the result (either a reflected presence update or a full join).
+Periodically do:
+* send a XEP-0199 ping IQ to your participant JID (it might get reflected to your client or to another one)
+* set a timer
+* if you receive a ping, respond to it
+* once you receive the ping response, you know you are still joined - stop the timer
+* if the timer fires, you are probably not joined any more
+** send presence unavailable
+** send join presence
 = MUC double join =