this is almost certainly a NAT issue. there are some combinations of NAT that preclude P2P communication. in particular, if one peer is behind a symmetric NAT, then if the other is behind a symmetric or a port-restricted cone NAT, P2P communication will not be possible.
try going to
from each of the peers. if at least one shows "No" for "Source UDP port number is preserved from orginal connection" and the other shows the same or a "No" for "can receive from different IP address, different UDP port number", then your P2P communication will probably not succeed across the Internet.
for more information on the issues surrounding NAT vs end-to-end communication in the Internet, please read this posting:
Thanks for the helpful pointers, Michael. It seems that we likely are running into NAT or firewall issues.
However, that leaves me wondering what on earth Cirrus can be useful for in the real world? I guess it is just possible that it might be useful in a large corporate campus where you can run multiple instances of an app on machines behind the same firewall; but for anything that is designed to be deployed on multiple end-user machines across the Internet it has no usefulness that I can see. In the real world, there is a huge mix of router and firewall configurations that the developer can have no control over: the P2P capabilities need to handle this without requiring end users to do nasty config work.
Adobe seems to have dropped the ball here: on the one hand, AIR apps can be easily installed and updated with a single button click; but if the new P2P capabilities are to work it seems we have to get end users to do nasty editing of configuration files to tunnel through NAT/firewall.
This is just not a subject that most Flex and AIR developers will have experience of so we really need some easy step-by-step instructions or better tools to enable us to make use of these capabilities in the real world!