UDP hole punching

[James]

I try to implement UDP hole punching according the excelent article
"Peer-to-Peer Communication Across Network Address Translators" from here -
http://www.brynosaurus.com/pub/net/p2pnat/.

It works fine on the same LAN but on the Internet I see that on each peer
the port is still blocked.
Here are some more details-
1. On the three computers, two peers and server, firewall is disabled.
2. There is a modern NAT router in every peer.
3. Each side sends to the other peer a packet every second(using the info
from server about the other peer datails).
4. Running Wireshark sniffer on each peer displayes similar results: the
sended packet to the other peer is decribed as OICQ protocol. Immediatly
following a second packet, prbably a respond from the peer NAT router,
described as ICMP packet, Destination unreachableIport unreachable.

Is there any idea why the hole punching doesn't work in this enviroment?
Regards
James

[Ronnny]

> It works fine on the same LAN but on the Internet I see that on each peer
> the port is still blocked.
> Here are some more details-
> 1. On the three computers, two peers and server, firewall is disabled.
> 2. There is a modern NAT router in every peer.
> 3. Each side sends to the other peer a packet every second(using the info
> from server about the other peer datails).
> 4. Running Wireshark sniffer on each peer displayes similar results: the
> sended packet to the other peer is decribed as OICQ protocol. Immediatly
> following a second packet, prbably a respond from the peer NAT router,
> described as ICMP packet, Destination unreachableIport unreachable.

The reason is the ICMP packets. It means that one of the router or both do
not support hole punching.
Ronny