[erlang-questions] Simple NAT traversal

Edward Wang <>
Wed Feb 1 14:37:28 CET 2012


A tcp server itself is simple enough, but that's another piece of
software running on a separated machine. That's a big disadvantage. On
the other hand, a UPnP control point is something you can integrate
into your own application, given your NAT device speaks UPnP and you
want to deal with the protocol.

-Edward

On Wed, Feb 1, 2012 at 9:19 PM, eigenfunction <> wrote:
> Thank you for the response. But before i wade into that territory,
> do you think it will be easier than just writing a tcp server?
> Anyway, i am going to check that out.
>
> On 1 Feb., 10:50, Edward Wang <> wrote:
>> If your NAT device supports UPnP, you can ask for its external address
>> using UPnP protocol. But there's nothing simple in it. UPnP is a
>> horrible protocol.
>>
>> That said, if you do want to try this, you can check out UPnP
>> implementation in etorrent. I did that about one year ago for opening
>> port mapping. The related source code are
>> (https://github.com/edwardw/etorrent/tree/master/apps/etorrent/src):
>>
>>     etorrent_upnp_sup.erl
>>     etorrent_upnp_proto.erl
>>     etorrent_upnp_net.erl
>>     etorrent_upnp_handler.erl
>>     etorrent_upnp_entity.erl
>>
>> They are quite standalone and complete UPnP implementation. Take a
>> look at how add_port_mapping is implemented:
>>    https://github.com/jlouis/etorrent/blob/master/apps/etorrent/src/etor...
>> It should be easy enough to add your own get_external_address
>> function, which is defined in following specification:
>>    http://upnp.org/specs/gw/UPnP-gw-WANIPConnection-v1-Service.pdf
>>
>> Regards,
>> Edward
>>
>> On Wed, Feb 1, 2012 at 4:25 PM, eigenfunction <> wrote:
>> > Hi everybody,
>> > i have an erlang application running behind a nat. Now i have come to
>> > a point where i need to know my public ip. I was thinking about
>> > running a tiny tcp server behind the nat whose sole purpose would be
>> > to send me my public ip. My question is this: isn't there a more
>> > simple alternative? Heck, even if i could determine the public ip of
>> > the NAT device without doing a "backflip" it will be enough for my
>> > case.
>> > Any idea?
>> > _______________________________________________
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>> > 
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>>
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