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From: chris@umcp-cs.UUCP (Chris Torek)
Newsgroups: net.unix-wizards
Subject: Re: AF_UNIX domain socket question.
Message-ID: <6144@umcp-cs.UUCP>
Date: Wed, 29-May-85 05:31:34 EDT
Article-I.D.: umcp-cs.6144
Posted: Wed May 29 05:31:34 1985
Date-Received: Fri, 31-May-85 02:26:06 EDT
References: <213@greipa.UUCP>
Organization: U of Maryland, Computer Science Dept., College Park, MD
Lines: 27

> Can several processes write to a unix-domain stream socket at the
> same time and preserve the 'atomic' nature of each call?

Yes, if you're lucky.

> Should I be using datagram sockets?

Probably.

> Even more important to this discussion, can several processes write
> to a socket without 'connecting' to it? I.E. calling socket and
> binding the descriptor to an existing socket (unix file) then reading/
> writing directly to the socket without calling connect. The reason
> being that I need to server to go into a read wait on a socket
> for data that could come from several processes at different times.
> I'd like to give each process its own socket in the usual way, but
> that means I'd have to go into an accept wait...

(Ignoring the fact that that AF_UNIX SOCK_DGRAMs are connectionless...)
Not true; you can use select to tell you which of the r/w sockets and/or
the original bound socket are ``readable''.  Select for reading succeeds
when the accept() system call will not block.  This is well-known in
a couple of servers and isn't likely to change....
-- 
In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 4251)
UUCP:	seismo!umcp-cs!chris
CSNet:	chris@umcp-cs		ARPA:	chris@maryland