rndz

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

The main idea is straightforward: using a rendezvous server to observe peers' addresses and forward connection requests. When both peers send packets to each other, the NAT device or firewall rule then allows the traffic through.

Usage

TCP Listen/Connect

Client 1

use rndz::tcp::Client;

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

Client 2

use rndz::tcp::Client;

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

Pair Two UDP Sockets

Client 1

use rndz::udp::Client;

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

Client 2

use rndz::udp::Client;

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

Testing

Rndz Server

$ rndz server --listen-addr 0.0.0.0:8888    # To allow clients to communicate with IPv6, use [::]:8888

Client 1

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

Client 2

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

Portability

Due to the reliance on socket options SO_REUSEADDR and SO_REUSEPORT behavior, and the connected UDP socket, it does not work on all platforms.

Tests pass on Linux; however, udp::Client::listen() does not work on Windows.

Used in Projects

• quic-tun: A QUIC-based port forward.
• minivtun-rs: A UDP-based VPN.
• rndz-go: Golang implementation of rndz.