[ENet-discuss] NAT punchthrough sample source code (yet again)?

[Lee Salzman]

In terms of trading addresses, the third-party must not be behind a NAT, and for that matter, it will see whatever global address is visible from the outside. That is exactly the address that you need and that is what it relays to both ends. Since ENet uses the same UDP socket for a given host, this address is all you need to trade.

For reference:

http://nattest.net.in.tum.de/results.php
http://think-like-a-computer.com/2011/09/16/types-of-nat/

If it's symmetric NAT you're just screwed anyway. There's no real fool-proof method of punching through symmetric NAT. Just have the user explicitly forward ports on his router and leave it at that. You'll save yourself endless hassle.

Otherwise, simple punch-through schemes follow from the description of how they work in that second link. Worst case requires sending some extra spurious packets out on the UDP socket of the hosts, but otherwise is almost as simple as the scenario I described in my first email.

The third-party is going to be different in different use-cases. There really is not going to be any one universal way to do it.

If you have a game networking setup based on a client-server architecture, then it is just more useful to completely ignore all this and have the user explicitly open ports on his router, IMO. So long as the server has forwarded ports, clients don't have to bother with any of this at all - they just connect to the server, the end.

On 05/04/2013 07:51 PM, Erwin Coumans wrote:
>>> Set up a third-party ENet host C. Hosts A and B connect to C. C gives A the address of B. A directly connects to B. A and B disconnect from C.
> I doubt this will work. What kind of addresses and ports are
> exchanged? The global IP addresses is different from a local IP behind
> a firewall.
>
> If NAT punchthrough were that simple, why would people use Libjingle for it?
> http://maemo.org/development/documentation/manuals/3-x/howto_use_stun_bora/
>
>
> It would be great if we can get a simple working sample source out of
> this tread,
> instead of long discussions how one could attempt to implement it.
> Thanks!
> Erwin
>
>
>
>>> There is no official sample, per se, but it perhaps bears repeating that a NAT punchthrough implementation is as simple as:
>>> Set up a third-party ENet host C. Hosts A and B connect to C. C gives A the address of B. A directly connects to B. A and B disconnect from C.
>
> On 05/04/2013 07:30 PM, Erwin Coumans wrote:
>> Hi,
>>
>> I found many discussions on the topic but
>> no working sample code for NAT punchthrough with enet.
>>
>> Is there any self-contained sample source that works with enet?
>> Thanks,
>> Erwin
>>
>>
>>
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