[JDEV] Dialup and laptop users, lost packets, and faulty presence info

[Nathan Sharp]

I've been pretty successfully running a 1.4.2 jabber server at our 
offices for a short while now and love having IM internal to our company 
w/o the big players.  I've got one major issue, though.  I've been 
trying to find past debates over this but have failed so far, so excuse 
me if this has already been discussed.  
The problem comes when a dialup or a laptop user pulls the plug on their 
network connection without ever logging off of jabber.  The jabber 
server won't notice until it tries to send a message to the client and 
gets a network error.  Unfortunately this is unreliable as is.  I've had 
users that I know are offline stay listed as online for as long as 12 
hours!  
To make matters much worse, when you send a message to a person in this 
state, you never get an error back telling you that your message failed 
to be delivered, although usually you can tell becuase the server will 
soon afterwards log the faulty connection off and the person will 
dissapear from your roster.

Personally I think the only possible way to deal with this is to have a 
heartbeat between the client/server (I'd be willing to bet that all the 
major IM systems do this, because they don't exhibit this problem). 
 Temas expressed some concern over scalability, but to me this problem 
is worth fixing at a small cost to scalability.  (In fact, it may help 
some because you will not have non-existent users taking up resources!)

Now, I'm willing to spend a small amount of time at least prototyping a 
solution for testing, although given all my other projects I don't have 
a lot of time.  So far, however, I've had a terribly frustrating time 
trying to gather enough documentation or sample code to even start. 
 What I've been trying to do is build a server component w/ jabberbeans 
(I'm fond of Java, but I could go with other solutions if they are 
better...) that would send out a packet to all online users once per 
configurable time period, and then kick off anyone it doesn't hear a 
reply from before the next heartbeat.  Ideally it could listen for 
messages and presence info from clients and skip a heartbeat if other 
messages have been received from the client during that heartbeat 
period, although I'm not clear if a component can listen globally like 
that or not.  

What I've got so far is a server component which runs and lists itself 
in the client's browser, but I'm pretty stuck past there because I've 
failed to find documentation on server components past that point (or 
even example server components).  In specific:
1a) Can I register with the server and have it send me presence 
information globally for everyone without having to have users 
explicitly register with me?
  - OR -
1b) If not I figure I can just query for all online users right when it 
comes time to send out the heartbeat, which I found how to do last night 
with an iq:browse to servername/admin.  However, jabberbeans doesn't 
have a ExtensionBuilder for that namespace.  Is there a way w/ 
jabberbeans to send custom xml or do I have to write my own 
ExtensionBuilder?

2) Can I globally listen to <message> packets coming from users without 
disturbing the normal delivery process?
3) I can always send a client version or time IQ to the client as a 
dummy packet for my heartbeat, but ideally I want the smallest message 
possible to which clients will respond to without any user intervention 
or knowledge.  (Sounds like a prime place for a JEP if this works out). 
 Does anyone have ideas on a particular message type to send?

I have more questions, but I haven't researched them yet, so I'll wait.  

Thanks!
   Nathan


-- 
Nathan P Sharp
Phoenix Integration
1715 Pratt Dr
Suite 2000
540-961-7215
540-961-5831 (fax)