[Twisted-Python] UDP File Copy

[Eugene Coetzee]

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.

Eugene

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