UDP not connecting on Mac OSX Leopard

[Alex Tweedly]

Jim Ault wrote:

Jim - I could preface each part of my reply with .... "Sorry I don't 
have a Mac w/ Leopard to check,"
> 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',
...check, but I wouldn't be surprised if that meant "allow incoming TCP 
connections", and there might be a separate setting for UDP.
> both computers have a static IP address,
> are connected to the internet using a switch (not a router)
>
No, I don't believe that. (Almost) no-one is connected to the Internet 
without a router - it's just a question of where the router is. Do you 
mean that the computers are both connected to a switch - and behind that 
is the router and Internet connection ? And therefore the two should be 
communicating locally ? 

> 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
>
Do you still have 10.4 systems around so you can try client on 10.4 and 
server on 10.5, etc. ?
> Can anyone shed some light on how to make this work?
Stupid question - does it work with client and server on the same computer ?
Are they on the same subnet ?
Can you do a ping from one to the other ?
How about a traceroute - just to check there is a direct connection ?
If you clear the arp cache, then run the client, does the sever then 
show up in the arp cache ?
   (in a terminal window - "arp -a" to see the cache, "arp -d -a" to 
clear it)


I'll try to find a Leopard system tomorrow to play with it ....

-- Alex.