[JDEV] server functionality

[Chandan Sonaye]

Hi all,

    I have read jabber document saying that jabber client inform his
presence by using 'presence tag'.
    Client can sends either "available" or "unavailable" info. through
presence tag like
    <presence type='unavailable'>.
     Now if he mentions 'unavailable', server doesn't send him any new
messages. Instead they are stored as offline messages.
    or if he mentions 'available', server sends him every new messages.

    So server should know presence info. of every client.
    How does server store this information?
    Does it keep a flag for presence for every user or is the case like
every user sends message 'i am present' periodically
    so that server should know?
    How exactly server handles presece information?

   Thank you,

  chandan