Launching an application: Does PHP limit network connections?

[vol30w60]

Hi folks,

I am having a problem using PHP to launch an application on the server.
All the basics work, but I cannot launch more than 4 instances of the
application. This application functions as a server itself, and I
specify the port number when I launch it, so my theory is that I am
reaching some limit on network connections.

This is my basic launch sequence:

<?php
$command = 'c:\\Program Files (x86)\\myprog\\myprogram.exe';
$arguments = ' /Port:' . $port;
exec('C:\\PsTools\\psexec.exe -accepteula -d -s "' . $command . '" ' .
$arguments . ' 2>&1', $output);
?>

Note that I am using psexec because I need to keep track of the process
ID number and kill the application when a user logs out. I can provide
more details if needed, but if there is indeed some upper limit on port
connections, that would certainly explain what I'm seeing.

Incidentally, if I try this same procedure launching "Internet
Explorer", my limit is 9 (instead of 4). If I launch a non-network
application, it seems that I can launch as many as I want without limit.

Note: I am using Windows XP Professional x64 Edition SP1