UDP packets to PC behind NAT

Grant Edwards grante at visi.com
Sat Sep 16 14:56:06 CEST 2006


On 2006-09-16, Janto Dreijer <jantod at gmail.com> wrote:
> Steve Holden wrote:
>> Note that TCP and UDP port spaces are disjoint, so there's no way for
>> TCP and UDP to use "the same port" - they can, however, use the same
>> port number. Basically the TCP and UDP spaces have nothing to do with
>> each other.
>>
>> Most dynamic NAT gateways will respond to an outgoing UDP datagram by
>> mapping the internal client's UDP port to a UDP port on the NAT
>> gateway's external interface, and setting a converse mapping that will
>> allow the server to respond, even though technically there isn't a
>> "connection". The NAT table entries will typically be timed out after a
>> short period of non-use.
>
> So are you saying one can't use TCP to punch a hole for UDP?

Yes, that's what he's saying -- or at least that there's no
reason to expect it to work.

-- 
Grant Edwards
grante at visi.com



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