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Message-ID: <384C3898.43BD108@ihug.co.nz>
Date: Tue, 07 Dec 1999 11:28:40 +1300
From: Ross Smith <ross DOT s AT ihug DOT co DOT nz>
Organization: The Internet Group
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To: cygwin AT sourceware DOT cygnus DOT com
Subject: Re: More than 64 sockets ?
References: <Pine DOT LNX DOT 4 DOT 10 DOT 9912052255370 DOT 691-100000 AT bono DOT reversers DOT net> <199912061554 DOT JAA15146 AT hp2 DOT xraylith DOT wisc DOT edu> <19991206161728 DOT C2223 AT cygnus DOT com> <19991206164843 DOT B9747 AT cygnus DOT com>
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Chris Faylor wrote:
> 
> On Mon, Dec 06, 1999 at 04:17:28PM -0500, Chris Faylor wrote:
> >On Mon, Dec 06, 1999 at 09:54:39AM -0600, Mumit Khan wrote:
> >>stefan <stefan AT linux DOT f1 DOT fhtw-berlin DOT de> writes:
> >>> Hello,
> >>>
> >>> we were porting a server software to Win9x/NT and had to notice that you
> >>> cannot accept() more than 64 sockets. Why is this ? Can anyone help us ?
> >>
> >>The underlying OS API, WaitForMultipleObjects, has a limit of 64 handles
> >>it can wait on, and that's probably the reason. There are tricks to get
> >>around it, but it requires creating multiple threads. Not pretty.
> >
> >This isn't a problem with cygwin.  Cygwin uses the Winsock select() for
> >sockets.  There probably is a limit there but it's not 64.
> 
> Just to clarify:  The "This" above refers to the WaitForMultipleObjects
> limit of 64 handles.  This particular hard limit probably does not affect
> cygwin.
> 
> There is a hard-coded limit in winsock.h which is probably what is coming
> to play here.

This section from the Winsock Programming FAQ may be relevant:

> 3.17 - Can I change FD_SETSIZE to make select() wait on more than 64
> sockets?
>
> You can, but in practice it may not work. Several common Winsock
> stacks and Layered Service Providers limit themselves internally to
> the default value of FD_SETSIZE, 64. However, you can write a test
> program to try this on the systems you plan on supporting, to see if
> they are not limited. Also, you can always send each group of 64
> sockets to a different thread, so that several calls to select() can
> occur simultaneously.

(http://www.cyberport.com/~tangent/programming/winsock/)

--
Ross Smith <ross DOT s AT ihug DOT co DOT nz> The Internet Group, Auckland, New Zealand
========================================================================
    "Be careful about using the following code -- I've only proven
    that it works, I haven't tested it."           -- Donald Knuth

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