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From: leh@atlantis.cis.ufl.edu (Les Hill)
Newsgroups: comp.unix.programmer
Subject: Re: Berkley sockets
Message-ID: <27642@uflorida.cis.ufl.EDU>
Date: 25 Mar 91 19:05:22 GMT
References: <1991Mar14.193619.21766@m.cs.uiuc.edu> <1991Mar13.190847.9755@watdragon.waterloo.edu> <1991Mar14.122151.21216@virtech.uucp> <16730@uudell.dell.com> <1991Mar19.202408.14706@m.cs.uiuc.edu>
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In article <1991Mar19.202408.14706@m.cs.uiuc.edu>, carroll@cs.uiuc.edu (Alan M. Carroll) writes:

|> There's a number of reasons for not doing it that way. The program
|> that I am writing is a "software bus", which accepts messages from a
|> set of clients, and routes those messages to the set of clients that
|> are interested in them. Each client connects to the bus via a scoket,
|> which is used to send messages to other clients, and receive them.
 
|> 3. Because of the nature of the program, data from any socket can have
|> a need to be sent to an arbritrary subset of all the other sockets. In
|> order to do this using child process, each child process would have to
|> have a means of communicating with either all the other child
|> processes (and detect when any of them exited), or with the parent
|> process which would then forward the messages. The former is too ugly
|> to even discuss*. The latter can't work, because it brings us back to
|> the original problem - how does the parent move the data when it's
|> hanging on an accept?
|> -- 
|> Alan M. Carroll                "I hate shopping with the reality-impaired"
|> Epoch Development Team                 - Susan
|> CS Grad / U of Ill @ Urbana    ...{ucbvax,pur-ee,convex}!cs.uiuc.edu!carroll

As it happens, I have just been putting the final touches on a library which uses
sockets to allow communications to any one peer or all peers; clearly, the leap to any subset is routine matter.  Ignoring the origins of this library for the moment,
the scheme I used could be modified from its completely distrubuted control system into a client/server system to meet your needs.  To give you the short answer, use select in your server (or software bus) and for every client use a SIGIO handler (obviously after setting the socket connection to the server for async.)  As the SIGIO handler is invoked read in the data from the server and store it, use a netread() (or some such routine) to access the stored data as your client needs it, writes can be made di







rectly to the server.  [Obviously, a protocol of some sort needs to be used between the clients and the server -- I am guessing that you already have most of it ironed out.]  If the idea of SIGIO scares you, you could use select or fork off a child that would handle the network connection (and communicate via a pipe or some such.)

-- 
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