Le mardi 05 avril 2005 à 15:31 -0400, Tom Carmichael a écrit :
UDP has it's place, but typically vanilla file transfer isn't it.
UDP traffic typically is harder to NAT rather than easier. Since it is a stateless protocol, what is meant by a 'reply'? How do you keep a forward and reverse translation table for the communications?
It is only harder for people who design NAT devices. ;) But the real difference here between UDP and TCP, is that when you open an outbound TCP connection, incoming TCP traffic will only be allowed *for that connection*. Whereas if you send an outbound UDP message, *all incoming UDP traffic* towards the originating address/port will be enabled (at least on some NAT boxes). This makes it easy for P2P systems to exchange messages between two NATted clients without any proxying/tunnelling mechanism: you just have to "punch a hole" by sending sporadic outgoing UDP traffic from your UDP socket and then you can receive all UDP traffic coming to that socket. You can't do that with TCP. Regards Antoine.