All the good, offered solutions so far are heavily geared by the idea of "time" (ie, connections per second). This is not what is being asked. The maximum connections limit is a per server parameter that controls, more or less, how many accept()ed TCP connections are there in the server side.

What ibanix needs to know, is if the server will process more than 100 concurrent connections in any time frame, which is not exactly the same problem.

In order to test this, execute this simple script (I called it nsock) and pay attention to what happens...

#!/usr/bin/perl

use strict;
use warnings;
use Getopt::Std;
use IO::Socket::INET;
use vars qw($opt_s $opt_p $opt_n);

getopts("s:p:n:");

die <<EOF
nsock -s server [-p port] [-n number]

-s: server to connect to
-p: port to connect to. Defaults to 80
-n: number of concurrent connections. Defaults to 100
EOF
    unless $opt_s;

$opt_p ||= 80;
$opt_n ||= 100;

my @socks = ();

$| = 1;

for my $c (1 .. $opt_n)
{
    print ">>> Socket #$c\n";
    my $s = new IO::Socket::INET->new
        (
         PeerAddr       => $opt_s,
         PeerPort       => $opt_p,
         Proto          => 'tcp',
         Timeout        => 30,
         );

    unless ($s)
    {
        warn "Failed to create socket $c: $!\n";
        sleep 2;
        redo;
    }

    print "<<< $c connected ok\n";
    push @socks, $s;
}

print "*** All concurrent connections done!\n";
[download]

What it does is simply, open a TCP socket to the desired server and keep it open. If you run it with slightly larger number of connections (say, 101) you should see the 101th connection take forever to establish. This happens because it is going into the accept() queue and not established right away.

If you run it with 100 connections, all of them should be established. Hope this helps.

Best regards

-lem, but some call me fokat