[Twisted-Python] UDP File Copy
projects at reedflute.com
Thu Apr 7 08:19:26 EDT 2005
Tommi Virtanen wrote:
>On Wed, 2005-04-06 at 11:18 +0200, Antoine Pitrou wrote:
>>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.
>You can't do that with NATted UDP, either. Quite many firewalls
>want to match all of the (srcIP, srcPort, dstIP, dstPort) to match.
Exactly. It depends entirely on what you do with NAT.
Some NAT boxes are stricter than others - but in principle I block
anything weird or undesirable - most notably protocol hacks of this
nature designed to circumvent firewalling.
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