Can a connection between "cone NAT with port restriction" and "symmetric NAT" be established without a third-party?

Question

Directly it's impossible, right?

Using an intermediate server isn’t an option because I have a requirement that says that a solution has to exchange lots of data and also be fast.

Although, creating a simple utility, if required, that’d run on both nodes locally and thus facilitates establishing a connection, would be ok.

It'll be a UDP connection.

How to do it?

NAT is one of the problems that IPv6 solved, and is a major reason why some services (*like the XBox gaming network) are IPv6-only. — Michael Hampton, Sep 06 '20 at 14:50
@MichaelHampton will using ipv6 alone in this case solve the problem? — mixtouku311, Sep 06 '20 at 15:56

Steffen Ullrich · Answer 1 · 2020-09-06T17:43:12.810

1

As you correctly determined, direct connection is impossible. One needs the help of an external relay reachable from both peers to transfer the data, i.e. TURN or similar. If you don't want to rely on a third-party you need to run this relay yourself. If you don't want this either, your problem can not be solved.

edited Sep 06 '20 at 17:43

answered Sep 06 '20 at 06:46

Steffen Ullrich

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will TCP vs UDP make a difference as of possiblity to establish a connection? – mixtouku311 Sep 06 '20 at 15:55
@mixtouku311: TCP is even worse, i.e. it will not work in cases where UDP still works. – Steffen Ullrich Sep 06 '20 at 15:56
`one needs the help of an external relay reachable from both peers` --> is this only in the initial stage? thereafter both computers will be able to exchange data directly? – mixtouku311 Sep 06 '20 at 16:22
@mixtouku311: No. The relay is there to transfer all data. I've updated the answer. – Steffen Ullrich Sep 06 '20 at 17:43

Can a connection between "cone NAT with port restriction" and "symmetric NAT" be established without a third-party?

1 Answers1