[stunnel-users] FD_SETSIZE still an option in stunnel 4.34?

Michal Trojnara Michal.Trojnara at mirt.net
Wed Nov 3 10:20:51 CET 2010

Saikat Chakrabarti wrote:
> 1) Does FD_SETSIZE still exist in Stunnel 4.34 and could it be a
> reason why I am seeing a limit on the number of people that can make a
> connection?

FD_SETSIZE is only used with select() on Unix.

Execute "stunnel -version" and check the output for "Sockets:POLL" or

> I already tried running stunnel after setting ulimit -Hn
> and ulimit -Sn to 4096, and it did not seem to make a difference.

You reached a resource limit.  You should rather check your logs for error
message in order to identify the resource and increase the limit.

You could read:

> 2) More noobish question - how do I set the FD_SETSIZE at compile
> time?  I saw in the troubleshooting that it said to do
> "-DFD_SETSIZE=4096" at compile time.  Is this something I should be
> adding in one of the Makefiles?

You don't need to do it.  It's possible on some operating systems, but
there's no portable way to do it.  Stunnel uses poll() instead of select()
since version 4.06 (released Dec 2004).

> Linux gomockingbird.com #1 SMP Tue Nov 10 16:12:12
> UTC 2009 i686 GNU/Linux

stunnel.mirt.net is also a linode.  8-)

Best regards,

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