Re: bonjour

[Alain Magloire]

Bonjour Girish

  I usually do not do Cc: a list a mail send to me, but since  I had other
emails close to the subject, I think the list is a good place and that
there are some knowledgeable people here that can be helpfull also.

>       My name is Girish and I am working on a mail client for mobile phones. I
> have a query regarding the lock (exclusive access lock) implementation. What
> exactly is the role of a mail client w.r.t. the locking?
> According to the specification, the lock is done by the POP3 server. does
> this mean that the client has no role in it?
> 
> Please do reply,

Yes, according to the RFC:
RFC 1939                          POP3                          May 1996
   Once the POP3 server has determined through the use of any
   authentication command that the client should be given access to the
   appropriate maildrop, the POP3 server then acquires an exclusive-
   access lock on the maildrop, as necessary to prevent messages from
   being modified or removed before the session enters the UPDATE state.
   If the lock is successfully acquired, the POP3 server responds with a
   positive status indicator.  The POP3 session now enters the
   TRANSACTION state, with no messages marked as deleted.  If the
   maildrop cannot be opened for some reason (for example, a lock can
   not be acquired, the client is denied access to the appropriate
   maildrop, or the maildrop cannot be parsed), the POP3 server responds
   with a negative status indicator.  (If a lock was acquired but the
   POP3 server intends to respond with a negative status indicator, the
   POP3 server must release the lock prior to rejecting the command.) 
> 

So when the client contact the POP3 server it is important that it
"downloads" the messages and close the connection.  Because while the
connection is on, no mail can be received.  Some wellknown pop3d server
(Qualcomm pop3d) goes around this by moving the mail to a secondary storage
to allows you to receive mail when the session terminates it moves back
the entire mail and append any new messsages.

C-client pop3d and GNU mailutils pop3d do it by the book an exclusive lock
is created (fcntl() and /var/mail/user.lock) the lock will not be remove
until the session is over.


--
alain