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From: Simon Wright <simon@pushface.org>
Newsgroups: comp.lang.ada
Subject: Re: copy constructor for sockets
Date: 25 May 2004 06:10:00 +0100
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tmoran@acm.org writes:

> >> socket to the task during the rendezvous, and let the task create
> >> a socket and do the socket-accept.

> >I know you can use select() or poll() to block until an accept()
> >would succeed, is that the idea?

>   Yes.  Have the server task poll (frequently) to see if an accept()
> would succeed, then rendezvous with the handler task which does the
> actual accept().

I was thinking of poll(2), which can be told to block indefinitely
until some event occurs: 'man 2 poll' says

       poll is a variation on the theme of select.  It  specifies
       an array of nfds structures of type
               struct pollfd {
                       int fd;           /* file descriptor */
                       short events;     /* requested events */
                       short revents;    /* returned events */
               };
       and  a  timeout  in  milliseconds.  A negative value means
       infinite timeout.  The field fd contains a file descriptor
       for an open file.

       (etc)

>   In this case, though, the server could start/call a task and not
> worry about whether the task blocks on the accept().  If it does
> block, then there's no browser calling and the server has nothing
> else to do anyway.  Eventually somebody surfs by, at which time the
> task hanging on the accept() does the accept() and immediately
> finishes its rendezvous and the server is allowed to go and prepare
> another acceptor task.

I think there could be a problem with this if there's some problem
such that the accept(2) fails immediately, I suppose you could raise
an exception in the rendezvous if so,

>   One more thing: if the server does the Get_Line, that suggests
> there's only one Get_Line per accept(), ie, no persistent
> connections.

I don't see that, so long as the server hands on the connected socket?

-- 
Simon Wright                               100% Ada, no bugs.