Create a pure-Rust UDT/UDP hole-punching implementation

knocte commented 5 years ago

By "pure rust" we mean: no other dependencies other than the Rust base class libraries (because we want this to work on all OSs: Linux, Windows, Mac, Android, iOS).

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jirislav commented 5 years ago

Hi there, I'd be interested into this.

But could you please specify more on the implementation?

I suppose you want both client & server to be implemented. So that the hole-punching scheme would look like this: Client A connects to publicly available server C. Client B connects to publicly available server C. Server C sends NAT IP and established port of A to B. Server C sends NAT IP and established port of B to A. A connects to B and vice versa. Server C is not needed for further A <-> B communication (as long as the connection is alive, thus at least periodically sending empty UDP data packets).

If the connection is lost, both A & B again connect to C to determine their NAT IPs & ports.

However, a few questions arises:

Should it be a Rust client library, or do you want an executable program?

If you want executable program, there is a few questions that arise:

Would be an command line interface enough for clients?
How would in that case A & B pair together? (would be enough e.g. that the first one would get some 6digit PIN and the second one would have to provide it?)
What would the program do specifically? It could e.g. forward ports from one to each other (e.g. A_HOST:22 -> B_HOST:8022 - enabling 'direct' SSH access for further port forwarding)

If you want a library, there is also a few questions to answer:

Is there already a hole-punching server implemented you want to use?
If not, do you require us to implemented also the server? Does it have to be in Rust?
What do you want the API to look like? I image some sort of object named HolePuncher (the naming is a subject for discussion), which takes IP & port of hole-punching server at construction, while providing methods like connect, which takes some sort of identifier of the other side you want to connect with and returns an established connection.

Have a good day!