Losing messages over lost connection xmpp

Question

i went through this question

Lost messages over XMPP on device disconnected

but there is no answer.

When a connection is lost due to some network issue then the server is not able to recognize it and keeps on sending messages to disconnected receiver which are permanently lost.

I have a workaround in which i ping the client from server and when the client gets disconnected server is able to recognize it after 10 sec and save further messages in queue preventing them from being lost.

my question is can 100% fail save message delivery be achieved by using some other way i know psi and many other xmpp client are doing it.

on ios side i am using xmppframework

Answer 1

One way is to employ the Advanced Message Processing (AMP) on your server; another one is to employ the Message Delivery Receipts on your clients.

The former one requires an AMP-enabled server implementation and the initiating client has to be able to tell the server what kind of delivery status reports it wants (it wants an error to be returned if the delivery is not possible). Note that this is not bullet-proof anyway as there is a window between the moment the target client losts its connectivity with the server and the moment the TCP stack on the server's machine detects this and tells the server about it: during this window, everything sent to the client is considered by the server to be sent okay because there's no concept of message boundaries in the TCP layer and hence if the server process managed to stuff a message stanza's XML into the system buffers of its TCP connection, it considers that stanza to be sent—there's no way for it to know which bits of its stream did not get to the receiver once the TCP stack says the connection is lost.

The latter one is bullet-proof as the clients rely on explicit notifications about message reception. This does increase chattiness though. In return, no server support for this feature is required—it's implemented solely in the clients.

Answer 2

go with XEP-0198 and enjoy...

http://xmpp.org/extensions/xep-0198.html

Answer 3

For a XMPP client I'm working on, the following mechanism is used:

• Add Reachability to the project, to detect quickly when the phone is having connectivity problems.
• Use a modified version of XEP-0198, adding a confirmation sent by the server. So, the client sends a message, the server confirms with a receipt. Later on, the receiving user will also confirm with a receipt. For each message you send, you get two confirmations, one from the server, one from the client. This requires modifications on the server of course.
• When the app is not connected to the XMPP server, messages are queued.
• When the app is logged in again to the XMPP server, the app takes all messages which were not confirmed by the server and sends them again.

For this to work, you have to locally store the messages in the app with three possible states: "Not sent", "Confirmed by server", "Confirmed by user"