UDP not connecting on Mac OSX Leopard

[Jim Ault]

I don't seem to be able to make the easy connections between Macs  
running OSX 10.5 using Alex Tweedly's companion stacks
UDP Echo Client
UDP Echo Server

I have set the fire wall in OSX to 'allow all incoming connections',
both computers have a static IP address,
are connected to the internet using a switch (not a router)

but UDP traffic between them does not test positive.
This has not been a problem in the past using OSX 10.4 (Tiger)

[1]
compiled - UDP Echo Client running as an app on computer B
UDP Echo Server in Rev 2.7.2 on computer A

[2]
compiled - UDP Echo Client running as an app on computer B
UDP Echo Server in Rev 2.9.0 on computer A

Can anyone shed some light on how to make this work?

Thanks,

Jim Ault
Las Vegas