in reply to Re: Chat server impossible with Perl?
in thread Chat server impossible with Perl?

How do I use threads to listen for new connections whilst maintaining responsiveness to existing ones

You may not need threads to do that. Although perlipc and perlfunc don't mention it, you can run select on a generic socket, at least on Unix. In more detail:

You open perlipc, find the section labelled 'Internet TCP Clients and Servers', and use the recipe to create a generic server socket: socket(), setsockopt(), bind(), listen(). You now build a bitmask and go into a select loop. (If you've not used select before, perlfunc explains how. select is a way of sleeping until there's some activity on one or more of any number of connections.) When select says there's something ready for your generic socket to read, it means there's an incoming connection attempt: so you accept the connection, flip a bit in your bitmask to represent the new connection, and go back to the top of your select loop. You're now in an interesting position: select will return when you're ready either to accept a new connection or to read data from an existing connection. So, if you can service an incoming packet quickly enough, a single fibre is all you need.

That said, I'd be fascinated to know how to share globs between Perl threads. I threw away a day's work earlier this week because Perl told me it couldn't be done and (as this was work time) I decided not to spend time trying to hack it. At the very least, this restriction should be documented in perlthrtut and/or threads::shared.


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Re^3: Chat server impossible with Perl?
by BrowserUk (Patriarch) on Feb 05, 2005 at 00:45 UTC
    I'd be fascinated to know how to share globs between Perl threads.

    Supersearch for a thread by me with a title including "threads" and "globs" for my initial experiments in doing this. Basically, you need to pass a "handle" to a glob through a shared variable in such a way that threads::shared doesn't stick it's nose in and reject you. Be warned: The technique I used there has problems.

    I've a couple of other ways of doing it that I am experimenting with, but I would rather keep them quiet till I've proven to myself that they can be used reliably.

    Perl threads have an undeservedly bad rep as it is, without me causing more problems sharing speculative ideas without checking them out first. (Which is why I'm not linking to the post in question--If you want to try it, your gonna have to do a little work:)

    Examine what is said, not who speaks.
    Silence betokens consent.
    Love the truth but pardon error.