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

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(Stable Message IDs)
(Am I still there?)
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= Am I still there? =
 
= 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.
 
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 =
 
= MUC double join =

Revision as of 22:41, 6 April 2018

Stable Message IDs

As of 2018, server implementations are required to keep the message ID when reflecting client messages. This can be determined by the presence of the 'http://jabber.org/protocol/muc#stable_id' feature on the MUC JID or MUC domain.

Ambiguities

http://mail.jabber.org/pipermail/standards/2014-April/028805.html

Introduces 'ofrom' Extended Stanza Addressing (XEP-33) type

in http://xmpp.org/extensions/xep-0045.html#enter-history, which is not found in XEP-33 (nor XEP-33s schema).

Matching Your Reflected Message

So you sent a message to a MUC and want to immediately display it as "on the way" (good UX). Some time later (usually within some seconds) you receive a message from the MUC which might or might not be your sent message.

Find out if a relfection is your actual message, in six easy steps! The message is your reflection if:

  1. you recently sent a message to the MUC, AND
  2. the received message is from your participant JID, AND
    1. the XEP-0359 origin ID matches (probably not a transport) OR
    2. the message ID matches (a nice MUC, but not required by the XEP) OR
    3. the message body matches (not conclusive, some MUCs auto-pastebin) OR
    4. the received message is the first line of the sent message (transports like IRC split multi-line messages into one-liners) OR
    5. the sent message is very long (>400 bytes) and the received message is a prefix of it (IRC transpors split very long one-liners too!)

(this mechanism doesn't cover MUCs which don't reflect the message ID and do autopastebin. Screw them!)

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, 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.

The "most viable" workaround is:

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

It's not specified what should happen if an entity sends an initial presence when it's already joined. Implementations should behave towards the joining entity like it successfully joined. That means, if a presence update containing an <x> element is received from a participant, the server should send back the full presence list, the requested amount of history and the room subject.

MUC PM messages are not distinguishable from other MUC messages

http://mail.jabber.org/pipermail/standards/2015-May/029819.html