[ENet-discuss] NAT punch-through

[Chris Meub]

There's more on it here: http://alumnus.caltech.edu/~dank/peer-nat.html

On Mon, May 2, 2011 at 10:27 PM, Josh Klint <jklint at leadwerks.com> wrote:

> So what you're saying is:
>
> Client - player who wants to play game
> Server - player who wants to host game
> Participant #3 (for lack of a better term) - program running on a dedicated
> server
>
> Client and Server both creates client hosts that connect to Participant #3,
> which is running at a known IP address, on a known port.
>
> Participant #3 gets Server's IP address and port, and sends this
> information
> to Client.
>
> Client uses this information to immediately connect to Server, using the IP
> address and port provided by Participant #3.
>
> Is that correct?  So really the only time you need this is when Server is
> behind a router.  If Server was a player plugged straight into a modem, or
> Server was a dedicated server, this would not be necessary.
>
>
> -----Original Message-----
> From: enet-discuss-bounces at cubik.org [mailto:
> enet-discuss-bounces at cubik.org]
> On Behalf Of Lee Salzman
> Sent: Monday, May 02, 2011 1:30 PM
> To: Discussion of the ENet library
> Subject: Re: [ENet-discuss] NAT punch-through
>
> Just create both hosts and open a normal ENet connection on both hosts to
> some third party server not behind a NAT. This server should then report
> the
> addresses to both of the hosts needing to take part in the connection. The
> hosts can then use these addresses to connect to eachother, but just make
> sure you connect immediately after, or the router may close down the port
> again. Once that's up, the normal ENet keepalive ping is probably good
> enough by itself to keep the connection open. This works because each ENet
> host maintains a single UDP socket for all its connections, so provided you
> are on an asymmetric NAT, once the initial connection to the third party
> opens the port, it should keep that port open provided you are servicing
> the
> connection regularly.
>
>
> Note this will only work with asymmetric NATs - as in the router opens a
> port that works for any remote client to connect back to, so even if A is
> behind NAT, and connects to B, another peer C can connect to the address
> opened for A. Symmetric NAT is hell and only lets B connect back to A, not
> C, and there's basically no sane way to punch through those.
>
> Exactly what the third party is really depends on your application, and it
> not something that belongs in ENet proper.
>
> On 05/03/2011 01:34 AM, Chris Meub wrote:
> > I am by no means an expert on the subject, but I am using a really basic
> form of NAT punch-through with Enet at the moment with a hobby project. I
> have 2 clients, one at home behind a consumer router, and 1 at the office
> behind a firewall. Both connect to a central server, and begin transmitting
> packets to the server. The server collates the packets into simulation step
> packets, and sends those back to each client. This system works fine and
> I've had no issues with our firewall or any routers.
> >
> > Now I imagine if you wanted to get rid of the central server, that would
> be another story. You would probably have to still use a central server for
> matchmaking and then do some trickery to figure out which IP+port each peer
> needed to start sending packets to in order to bypass the firewall(s). But
> I
> imagine one could still do that with Enet.
> >
> > The only other thing I can think of would be some kind of brute force
> library that randomly tries ports until it finds one that can get through
> the firewall. Is that what RakNet provides?
> >
> > On Mon, May 2, 2011 at 1:32 PM, Josh Klint <jklint at leadwerks.com
> <mailto:jklint at leadwerks.com>> wrote:
> >
> >     Hi,
> >
> >     A search for enet and NAT punch-through yields a lot of questions
> about whether this is possible and discussion of how it might be done, but
> I
> have never found an actual instance of working code, or anyone who claims
> to
> have successfully implemented NAT punch-through with enet.
> >
> >     I love the simplicity of enet, but without NAT punch-through support,
> I don't see how it is useful for networked software.  I'll have to
> (unfortunately) go with RakNet, which is huge, bloated, and comes with
> licensing hang-ups I have to pass on to my customers.
> >
> >     Best Regards,
> >
> >     Josh Klint
> >
> >     CEO
> >
> >     Leadwerks Software
> >
> >
>
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