Alice from Device A sends 10 messages to Bob who has devices B and C (Both Offline).
The sent 10 messages to stay in the offline message queue.
As per, xep-0160, the first device (suppose B) that sends a positive presence gets the offline message delivered and then removed.
How the other device C will get the messages delivered to it then?
There is MAM or another pull-based mechanism for fetching from clients.
But is this intended by design or any config available that will keep offline messages until it gets delivered to all or number of the latest N device?
How the other device C will get the messages delivered to it then?
XEP-0160 doesn't care about multiple devices. As you noticed, once it sends the offline messages to a client, that's all for it.
But is this intended by design or any config available that will keep offline messages until it gets delivered to all or number of the latest N device?
That makes little sense: how would the server determine that YOU, Alice, only plan to have 2 devices, and Bob "plans" to have three?
That problem is already solved: XEP-0160 delivers the offline messages automatically to the first session that logins with possitive presence. MAM stores those messages in the account MAM archive. Whenever (if ever at all) any other session logins to that account, that client can request the recent MAM archive to know the recently delivered messages.
Related
I am using ejabberd server and ios xmppframework.
there are two clients, A and B.
When A and B are online, A can send message to B successfully.
If B is offline, B can receive the message when B is online again.
But when B is suddenly/unexpectedly lost connection, such as manually close wi-fi, the message sent by A is lost. B will never
receive this message.
I guess the reason is that B lost connection suddenly and the server still think B is online. Thus the offline message does work under this condition.
So my question is how to ensure the message that sent by A will be received by B? To ensure there is no messages lost.
I've spent the last week trying to track down missing messages in my XMPPFramework and eJabberd messaging app. Here are the full steps I went through to guarantee message delivery and what the effects of each step are.
Mod_offline
In the ejabberd.yml config file ensure that you have this in the access rules:
max_user_offline_messages:
admin: 5000
all: 100
and this in the modules section:
mod_offline:
access_max_user_messages: max_user_offline_messages
When the server knows the recipient of a message is offline they will store it and deliver it when they re-connect.
Ping (XEP-199)
xmppPing = XMPPPing()
xmppPing.respondsToQueries = true
xmppPing.activate(xmppStream)
xmppAutoPing = XMPPAutoPing()
xmppAutoPing.pingInterval = 2 * 60
xmppAutoPing.pingTimeout = 10.0
xmppAutoPing.activate(xmppStream)
Ping acts like a heartbeat so the server knows when the user is offline but didn't disconnect normally. It's a good idea to not rely on this by disconnecting on applicationDidEnterBackground but when the client looses connectivity or the stream disconnects for unknown reasons there is a window of time where a client is offline but the server doesn't know it yet because the ping wasn't expected until sometime in the future. In this scenario the message isn't delivered and isn't stored for offline delivery.
Stream Management (XEP-198)
xmppStreamManagement = XMPPStreamManagement(storage: XMPPStreamManagementMemoryStorage(), dispatchQueue: dispatch_get_main_queue())
xmppStreamManagement.autoResume = true
xmppStreamManagement.addDelegate(self, delegateQueue: dispatch_get_main_queue())
xmppStreamManagement.activate(xmppStream)
and then in xmppStreamDidAuthenticate
xmppStreamManagement.enableStreamManagementWithResumption(true, maxTimeout: 100)
Nearly there. The final step is to go back to the ejabberd.yml and add this line to the listening ports section underneath access: c2s:
resend_on_timeout: true
Stream Management adds req/akn handshakes after each message delivery. On it's own it won't have any effect on the server side unless that resend_on_timeout is set (which it isn't by default on eJabberd).
There is a final edge case which needs to be considered when the acknowledgement of a received message doesn't get to the server and it decides to hold it for offline delivery. The next time the client logs in they are likely to get a duplicate message. To handle this we set that delegate for the XMPPStreamManager. Implement the xmppStreamManagement getIsHandled: and if the message has a chat body set the isHandledPtr to false. When you construct an outbound message add an xmppElement with a unique id:
let xmppMessage = XMPPMessage(type: "chat", to: partnerJID)
let xmppElement = DDXMLElement(name: "message")
xmppElement.addAttributeWithName("id", stringValue: xmppStream.generateUUID())
xmppElement.addAttributeWithName("type", stringValue: "chat")
xmppElement.addAttributeWithName("to", stringValue: partnerJID.bare())
xmppMessage.addBody(message)
xmppMessage.addChild(xmppElement)
xmppMessage.addReceiptRequest()
xmppStream.sendElement(xmppMessage)
Then when you receive a message, inform the stream manager that the message has been handled with xmppStreamManager.markHandledStanzaId(message.from().resource)
The purpose of this final step is to establish a unique identifier that you can add to the XMPPMessageArchivingCoreDataStorage and check for duplicates before displaying.
I guess the reason is that B lost connection suddenly and the server
still think B is online. Thus the offline message does work under this
condition
Yes you are absolutely correct,this is well known limitation of TCP connections.
There are two approaches to your problem
1 Server side
As I can see you are using ejabbed as XMPP server you can implement
mod_ping , Enabling this module will enables server side
heartbeat[ping] ,in case of broken connection to server[ejabbed] will
try to send heartbeat to connection and will detect connection is lost
between server and client. Use of this approach has one
drawback,module mod_ping has property called ping_interval which
states how often to send heartbeat to connected clients, here lower
limit is 32 seconds any value below 32 is ignored by ejabbed,means
you have 32 seconds black window in which messages can be lost if user
is sowing as online
2 Client side
From client side you can implement Message Delivery Receipts
mechanism .With each Chat message send a receipt to receiver user of
as soon as receiver user receives message send back this receipt
id. This way you can detect that your message is actually delivered to
receiver. If you don't receive such acknowledgement between certain
time interval you can show user as offline locally(on mobile
phone),store any further messages to this user as offline message
locally[in SQLLight database ],and wait for offline presence stanza for that user
,as soon as you receive offline presence stanza it means that server
has finally detected connection to that user is lost and makes user
status as offline ,now you can send all messages to that user ,which
will be again stored as offline messages on server.This is best
approach to avoid black-window.
Conclusion
You can either use Approach 2 and design you client such way ,you can also use Approach 1 along with approach 2 to minimize server broken connection detraction time.
If B goes offline suddenly then user A have to check if B is online/offline while sending message to user B. If user B is offline then user A have to upload that message on Server using Web service. And user B have to call web service on below function.
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
So user B will get that all offline message which was lost due to connection Lost.
At last, I use Ping together with Stream Management:
http://xmpp.org/extensions/xep-0198.html
This problem is solved.
Same user logged in three device(User name "A"), if a message is send to
this user(User name "A") from another user(User name: "B") only one
devices is receiving the messages other two devices are not receiving.
Kindly provide me a solution.
User A's clients and user A's server should implement XEP-0280, which does exactly that: it makes sure every connected client gets every received and sent message.
In case the message is sent to the full JID (i.e. user#domain/resource) there is no way to make other devices of the same user (but with a different resources) to receive the same message. This could be only possible if the XEP-0280 aka "Message Carbons" is implemented (this is what xnyhps suggested).
In case when the messages is sent to the bare JID (i.e. user#domain), it's usually sent based on presence priorities (f.e. it's true for Ejabberd), if all devices have the same presence priority the message will be sent to all the devices. It could not be true for your server, RFC 6121 says only about delivering to the "most available" resource, so everything depends on implementation:
delivering the message to the "most available" resource or resources according to the server's implementation-specific algorithm, e.g., treating the resource or resources with the highest presence priority as "most available" (M)
If you develop your custom client and aren't going to use any 3rd-party clients in your chat-system, it could be ok to not use carbons and just stick to the default server option of the message delivery. At least for the first time.
Actually we are using ejabberd server for one of our client's Chat application. Everything is working well except for Group chat.
We are using MUC for Group chat but it is not sending Messages to the member whenever uses is offline. Is there any alternative plugin or something where we can make that working?
Or any one can suggest about how to receive offline messages for that user from Group chat history.
Thanks in advance
That's because there's no such concept for multi-user chat rooms. In fact, if you'll think about this a bit more you'll understand why:
Potentially unbound number of participants might be present in a room at any given time.
So exactly for which users not currently present in the MUC room should the server store the messages in the offline storage? I mean, in the generic case, the server does not know all the users who could ever possibly chat in a given room it hosts.
(Well, if this would be the only problem, it could possibly work for members-only rooms, I must admit.)
MUC rooms are not "local server only": a potentially unbound number of users from any number of other servers might join the room, and messages to those users will be delivered by routing them via their respective servers.
Obviously, this is another reason why such an idea of "MUC room offline storage" has no sense.
MUC rooms are by definition transient: when a user is offline, they're not in any room— (re-)joninig a room is an explicit action.
This is in fact the most important reason for not supporting offline storage.
As you can see, XMPP MUC rooms are much like IRC chats on steroids.
So what you really want is "room history"—a part of the XMPP-0045 extension which allows the client to explicitly ask the room for the message history they missed. In a sense, instead of storing offline message for each user, the room might be configured to store just a certain number of the most recent messages sent to it (or all such messages for a given period of time). Then the room supports querying these messages by the joined users.
There's another possibility which you might explore: "multicast addressing" of XEP-0033 ("Extended stanza addressing"). Basically it allows a client to use a special multicast service to send their message to multiple recipients at once. The upside is that offline storage is there again. The downside is that I doubt such a multicast service is supported out of the box in ejabberd, and it seems like that extension leaves much details about how it could be implemented unspecified.
I faced your issue as I sought to implement groupchats for my chatting app. I faced the same problem of MUC not storing offline messages for each recipient. And I did not want to retrieve MUC history which requires the user to rejoin every MUC to update his messages database. What I wanted is for the server to save offline messages by recipient, and for the recipient to get all MUC messages when he gets online (without having to join each MUC).
The way I did it is through pubsub. Using pubsub will force the server to store offline message per recipient. When the user reconnects, he gets all the offline messages including the pubsub messages which are sent as normal messages - that is it. One issue I had with pubsub over MUC though is that it is hard to get the list of subscribers. So when my app creates a groupchat, it creates a pubsub node for messages, invite all participants to subscribe (including self) to the pubsub and my app also creates a MUC and makes every participant an owner of that MUC. This way the list of the groupchat participants can be retrieved by checking the list of owners of the MUC. The only purposes of the MUC are to hold the list of participants as well as the name of the groupchat. Everything else is handled by the pubsub node.
Anything unclear please let me know.
ADDITIONAL DETAILS:
Essentially when the user wants to create a groupchat, our app creates a pubsub node as well as a MUC. You need to be familiar with both concepts. For the pubsub node, you need to set an option to allow any subscriber to post. When a user sends a message, he actually publishes on the node, and ejabberd will send the message to all subscribers as if it were a regular message (except it comes from pubsub.yourdomain.com). Therefore if a recipient is offline, ejabberd will store this message as any other regular message.
This is not how ejabberd handles MUC messages. Those are only sent to people CURRENTLY in the chatroom. History of messages can be stored by ejabberd however, but for a recipient to get the history he will need to join the MUC. Which means that everytime the app reconnects, it would have to join all the user's existing MUCs. We found this was not practical.
We also use a MUC for the same groupchat, but this is only to store participants so that a user can get the list at any time (no way to do it with pubsub).
An additional benefit of using pubsub over MUC is that the way ejabberd stores pubsub data is way more efficient. I have not studied this in depth, but I expect much better performance from pubsub.
New ejabberd server at 16.09 version have improvements for multi-user chat - MUC Sub:
The goal of MUC Sub is to try to rely as much as possible on existing MUC specification, while making the smallest possible change that make mobile group conversation client easy.
The feature is enabled by default. To use it, just make sure you set the new parameter “Allow subscription” in the room on which you want to use it.
Here is link to documentation: https://docs.ejabberd.im/developer/proposed-extensions/muc-sub/
More info here: https://blog.process-one.net/xmpp-mobile-groupchat-introducing-muc-subscription/
I'm wondering how (official) GTalk clients manage to show all messages received - even if it was originally consumed by another client. For example: I'm logged into GTalk on gmail.com on my laptop and, at the same time, via the official GTalk app on my Android device. A friend sends me a message, which is displayed on both the gmail.com client and the Android client. (I think it's originally only forwarded to one of either clients, but the second client fetches the message later on)
I recently found out that there's a very similar XMPP feature, called Carbons. However, after a quick service discovery request Google's servers didn't advertise this feature. XEP-0313 and XEP-0136 look good too, but the servers don't advertise them either.
Possibly related question: Deliver Google Talk message to all logged in clients using XMPPPY
When you initiate a new chat then you should send the first message to the users bare Jid. This is what most clients are doing. When the GTalk server retrieves a chat message to a bare Jid it routes the message to all available resources. For all following messages in this conversation the clients normally pick up the Resource and send them to full Jids. The messages should not be replicated then.
Many other servers don't route message to bare Jids to all resources, but to the most available resource which is the client with the highest priority.
Here is a quote form the RFC:
If there is more than one resource with a non-negative presence priority then the
server MUST either
(a) deliver the message to the "most available" resource or
resources (according to the server's implementation-specific algorithm, e.g., treating
the resource or resources with the highest presence priority as "most available") or
(b) deliver the message to all of the non-negative resources.
XEP-0280 defines this. As I understand, it defines the mechanism to notify all the resources from same user when one of them sends a message to anyone. I mean, Alice/pda sends a message to Bob, so Alice/mobile and Alice/PC will receive a copy of the message sent be Alice/pda.
Hope it helps. I am currently looking for a server that implements this, and also for a client library. If not, I will implement it by myself in both jabberd2 and gloox xmpp library.
Cheers,
I am basically writing a XMPP client to automatically reply to "specific" chat messages.
My setup is like this:
I have pidgin running on my machine configured to run with an account x#xyz.com.
I have my own jabber client configured to run with the same account x#xyz.com.
There could be other XMPP clients .
Here is my requirement:
I am trying to automate certain kind of messages that I receive on gtalk. So whenever I receive a specific message eg: "How are you" , my own XMPP client should reply automatically with say "fine". How are you". All messages sent (before and after my client replies) to x#xyz.com but should be received by all clients (my own client does not have a UI and can only respond to specific messages.).
Now I have already coded my client to reply automatically. This works fine. But the problem I am facing is that as soon as I reply (I use the smack library), all subsequent messages that are sent to x#xyz.com are received only by my XMPP client. This is obviously a problem as my own client is quite dump and does not have a UI, so I don't get to see the rest of the messages sent to me, thereby making me "lose" messages.
I have observed the same behavior with other XMPP clients as well. Now the question is, is this is a requirement of XMPP (I am sorry but I haven't read XMPP protocol too well). Is it possible to code an XMPP client to send a reply to a user and still be able to receive all subsequent messages in all clients currently listening for messages? Making my client a full fledged XMPP client is a solution, but I don't want to go that route.
I hope my question is clear.
You may have to set a negative presence priority for your bot..
First thing to know is that in XMPP protocol every client is supposed to have a full JID. This is a bare JID - in your case x#xyz.com with a resource in the end e.g. x#xyz.com/pidgin or x#xyz.com/home (where /pidgin and /home are the resource). This is a part of how routing messages to different clients is supposed to be achieved.
Then there are the presence stanzas. When going online a client usually sends a presence stanza to the server. This informs about e.g. if the client is available for chat or away for lunch. Along with this information can be sent a priority. When there are more than one clients connected the one with the highest priority will receive the messages sent to the bare JID (e.g. ClientA(prio=50) and ClientB(prio=60) -> ClientB receives the messages sent to x#xyz.com). But there are also negative priorities. A priority less than 0 states that this client should never be sent any messages. Such a stanza might look like this
<presence from="x#xyz.com/bot">
<priority>-1</priority>
</presence>
This may fit your case. Please keep in mind it also depends on the XMPP server where your account is located, which may or may have not fully implemented this part of the protocol.
So to summarize: I recommend you to look through the Smack API how to set a presence and set the priority to <0 for your bot client right after it connected.