number of simultaneous connections

From: Torsten Valentin (
Date: Mon Sep 16 2002 - 11:42:24 CEST


I am planning to use PEN in a setup where a really large number (10.000)
of clients are holding simultaneous connections to a set of servers. The
connection type is ssl, the individual sessions remain up for hours
(80%), days (15%) and in some cases (5%) months. The sessions have a
keepalive-command every 8 minutes, so there's a minimal load of 21
packets a second, which is really not much and should not be a problem
at all. Average and maximum load are no problem either. The only problem
that I see is the large amount of simultaneous connections.
I saw the configure-flag --with-fd_setsize=N. What limitations are
there? Can I set this to 20000 without any further modifications? The
manual says there might be limitations by the OS, what are they? Is that
the maximal number of file-descriptors determined by the OS?

I tried (on OpenBSD 3.1) to compile with --with-daemon
--with-fd_setsize=20000. No compilation errors occurred.

How many simultaneous connections can I expect to work now?
Running pen with -C and sending "conn_max" returns 256, is that the

I tried to test pen and I can acknowledge that pen worked on my
OpenBSD3.0 and 3.1 with some tests.



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