Interprocess communication on multi-user machine

Lawrence D'Oliveiro ldo at geek-central.gen.new_zealand
Fri Jun 30 12:54:22 CEST 2006


In article <e82tbu$grc$1 at gemini.csx.cam.ac.uk>,
 nmm1 at cus.cam.ac.uk (Nick Maclaren) wrote:

>In article <ldo-619CD3.21214330062006 at lust.ihug.co.nz>,
>Lawrence D'Oliveiro <ldo at geek-central.gen.new_zealand> writes:
>|> In article <44a41cae$0$29145$9b4e6d93 at newsread4.arcor-online.net>,
>|>  Michael Butscher <mbutscher at gmx.de> wrote:
>|> 
>|> >Normally any user could connect to an open socket on a machine 
>|> >regardless which user established the socket (the user's program, to be 
>|> >precise). 
>|> 
>|> That's not true. On *nix systems, a socket is a file, and is subject to 
>|> the usual file ownership and protection mechanisms.
>
>I am afraid that BOTH answers are badly wrong!
>
>Sockets are often accessed via special files, but are not files.

They are files. They are not _regular_ files.

>They may also be accessed by port numbers, for example.

UNIX sockets have no ports.

>Secondly, even when they are accessed via files, FIFOs generally
>do NOT use the usual file ownership and protection mechanisms to
>control access.

I wasn't talking about FIFOs. Even if I was, they _are_ still subject to 
regular file permissions (on Linux, at least).

>While any user can attempt to open any socket accessed by port
>number...

UNIX sockets have no ports.



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