socket.recvfrom() & sendto()

Steve Holden sholden at holdenweb.com
Wed May 9 04:08:42 CEST 2001


"Ron Johnson" <ron.l.johnson at home.com> wrote ...
> Steve Holden wrote:
>
> > "Ron Johnson" <ron.l.johnson at home.com> wrote in ...
> > [ ... ]
> >>
> >> It seems like the server *and* the client both must use asyncore.
> >> But does asyncore, underneath it all, sit at select.select() waiting
> >> on the next readable socket?  So if the client is also using asyncore,
> >> does it need a thread for network IO and a thread for user interaction,
> >> and the 2 threads talk to each other?
> >>
> > Nope. The advantage of asyncore, and Medusa, is that you don't *need*
> > separate threads. You create a separate object for each dialog
> > (connection), which holds the stat information for that connection, and
> > the whole program just becomes one big select() loop, where each
> > connection object is told when there is data to be read, when it can
> > write, and so on.
> >
> > So it's a single thread, processing multiple objects asynchronously,
> > depending on events which are detected by the use of select().
> >
> > When you start, it's about as weird as your first GUI-based program --
> > event-driven programs are held together by string!
>
> Interesting.
>
> Since the server can send messages to the client at random and
> irregular interevals, how can the client accept input from the
> user at the same time that it is "stalled" at a select() ?
>
Under Unix I *believe* that select() can treat a tty channel like a socket,
but under Windows I understand that select() only works on sockets. One
possibilty (not perhaps the best one) would be to make your client module
receive input from a separate user interface module over a local (loopback)
socket, which would put user input on a par with network  input at the
expense of some structural inconvenience.

> The server side I think I understand, at least from the perspective
> of *my* needs: the server sits at a select() until it detects (an)
> incoming message(s) from client(s); it then processes the message,
> sends messages back to the sending client(s) and also possibly other
> clients, then goes back to the select().
>
That's the ticket.

regards
 Steve





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