[Standards] Application-level delivery notification between server and client

Kim Alvefur zash at zash.se
Wed Aug 7 08:32:40 UTC 2013

On 2013-08-06 22:15, Daniele Ricci wrote:
> Please correct me if I'm wrong at any point, just to be sure I
> understand XEP 198 and how I can use it in the right way.
> First of all, in this:
> "the client or server can send ack elements at any time over the stream"
> this means that I can send <a/> or <r/> just for message stanzas.

You're wrong.  XMPP requires in-order delivery of stanzas.  TCP
guarantees that things are received in the same order as they are sent.
 When you send <a h='x'/>, that means that you received all stanzas up
to number x.  The other end knows how many stanzas it sends, so it knows
which are acked and which are not.

Therefore, you can't ack "just for message stanzas", as you actually ack
all stanzas up to that point.

I hope this makes sense.

Kim "Zash" Alvefur

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