I may be wrong, but I wasn't aware of any arbitrary maximum number of  
connections possible, even on a non-server version of Windows.

Your message _seems_ to be saying that you are using a thread pool thread  
to create each connection.  If by that you mean that each connection has  
its own thread pool thread, then it seems likely to me that you're  
actually running out of threads, not connections.

If you want to host a large number of multiple connections, you need to  
avoid a "one thread per connection" implementation.  That technique will  
always unnecessarily limit the number of connections you can have at once,  
and performance will suffer even before you reach that limit.

Instead, look at the asynchronous API on the Socket class (or TcpClient  
and Stream if that's what you're using), where you call methods with  
"Begin" and "End" as part of the names.  For example,  
Socket.BeginConnect() and Socket.BeginRead().  These methods provide a  
much more scalable and efficient way of managing multiple connections with  
the same parallelism that multiple threads would give you, but without the  
limitations.  (In fact they do use threads themselves, but in a much more  
efficient way than dedicating one to each connection).

If I've misunderstood your architecture, then you should probably post a  
concise-but-complete example of code that illustrates what you _are_  
doing.  It's too easy to misunderstand a human language description of an  
implementation, but code is code.  :)

Pete

Hi,

You can either be running out of TCP connections (which I do not think ) or
of threads (which I think is the cause of your problem). Try to increase the
number of threads.

I'd like to thank everyone for a quick response and for sharing their
insight.
I just stumbled across this: http://forum.emule-project.net/lofiversion/index.php/t56016.html

It describes that XP SP1 has an unlimited of TCP client connection
requests whereas SP2 only allows 10 per second.
I've implemented a counter that increments on the request, and
decrements when connected. If the counter should reach 10, that thread
sleeps for a maximum of 1000ms waiting for a valid connection or
timeout. Whichever comes first.
It seems to work fine now, but will be running more test to confirm
these findings. Stay tuned.

Thanks again.

Greg

The magic setting you're looking for is "MaxUserPort". You can google this,
then make the appropiate registry change.

Thie value is typically set at 5000, and if you want lots and lots of client
connections then you need to bump the value up.

--
Chris Mullins