README.md

rndz

A simple rendezvous protocol implementation to help NAT traversal or hole punching.

The idea is simple, a rendezvous server to observe peers address and forward connection request. When seen both peers sent each other packet, the NAT device or firewall rule then allow the traffic through.

Under the hook, We create two socket bind to the SAME port number, one communicate the rendezvous server, the other communicate the remote peer. For tcp, the OS should allow listen socket and client socket with same port number coexist. For udp, the OS should correctly dispatch traffic to connected and unconnected udp with same port number respectfully.

tcp listen/connect

client1

use rndz::tcp::Client;

let c1 = Client::new(rndz_server_addr, "c1", None)?;
c1.listen()?;
while let Ok(stream) = c1.accept()?{
//...
}

client2

use rndz::tcp::Client;
let c2 = Client::new(rndz_server_addr, "c2", None)?;
let stream = c.connect("c1")?;

pair two udp socket

client1

use rndz::udp::Client;

let c1 = Client::new(rndz_server_addr, "c1", None)?;
c1.listen()?;
c1.as_socket().recv_from(...)?;

client2

use rndz::udp::Client;
let c2 = Client::new(rndz_server_addr, "c2", None)?;
c.connect("c1")?;
c.as_socket().send(b'hello')?;

test

rndz server

$ rndz server --listen-addr 0.0.0.0:8888    //if you want client communicate with ipv6, use [::]:8888

client1

$ rndz client --id c1 --server-addr rndz_server:8888 

client2

$ rndz client --id c2 --server-addr rndz_server:8888 --remote-peer c1

portability

Because it rely on socket option SO_REUSEADDR and SO_REUSEPORT behavior, and connected UDP socket, it doesn't not work on all platform.

Test pass on linux; udp::Client::listen() not works on windows..

used in projects

quic-tun minivtun-rs