More than 64 sockets ?

Chris Faylor
Mon Dec 6 13:46:00 GMT 1999

On Mon, Dec 06, 1999 at 09:54:39AM -0600, Mumit Khan wrote:
>stefan <> 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.

64 is just a hard-coded limit.  Recent snapshots should allow more than
this.  You have to set FD_SETSIZE to some other number.  Take a look at

>Go to the MSDN docs on and search for 64 *and* Wait
>and see if it turns up; also, search
>on, where this is usually beated to death.  Look for the
>article by Richter that shows the multiple thread implementation, where
>each new thread is started to handle the extra batches of 64 handles to
>wait for -- this is something Cygwin should implement (uh oh, do I hear
>the "feel free to submit patches" response ;-).

I don't think we really need this.  Most of the interesting fds are
already handled in separate threads.


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