webrtc-demo-client: A demonstration Rust WebRTC client

DISCLAIMER

This is messy, ugly, hastily written code that is nowhere near my usual standards, even for experiments. This code was written in such a way to answer one question as quickly as possible: Is the work-in-progress webrtc-sctp crate in its current state sufficient to demonstrate WebRTC data channel interoperability with a web browser, even though it lacks critical functionality and the required SCTP extensions? I arrived at the answer (yes -- though perhaps barely!) by stringing together the barest possible implementations of the other required WebRTC puzzle pieces (SDP parsing, ICE, STUN) and associated plumbing.

There are a number of hacks and shortcuts taken:

1. The client, server, and peer web browser are expected run on the same host.
   • No external STUN servers are queried for this client's server-reflexive address, and only "host" ICE candidates are regarded.
   • The client only considers the first non-loopback IPv4 address as its sole ICE candidate.
   • The client only considers peer ICE candidates that match the above IP address exactly. (Due to this and the above, I'd not recommend performing this demo on a machine with multiple non-loopback IPv4 addresses configured. In other words, don't have a VPN running.)
2. The DTLS Client Hello is not sent immediately after an ICE resolution; the demo instead delays one second and then tries to initiate DTLS. (The delay is noticeable in the demo.)
3. The client doesn't verify the certificate fingerprint of the peer.
4. There are lots of unwrap()'s. If anything goes wrong in the slightest way, the demo panics.

How to run the demo

NOTE: At this time, I've only tested this demo on Mac OS 10.11.6 and Ubuntu 18.04. I don't know of any particular problems that would arise on other operating systems, but I suppose there's a possibility that some dependencies (e.g. openssl and get_if_addrs) might not work as I expect.

On Ubuntu 18.04, I needed to install a few extra packages to satisfy the openssl crate:

sudo apt install build-essential libssl-dev pkg-config

Building on Mac OS likely has similar requirements. (Development tools? The Homebrew OpenSSL package?) I'm not sure of the exact requirements, though, since my Macs would have already had those things installed.

Three crates need to be cloned from GitHub:

1. webrtc-demo-client -- This client crate.
2. webrtc-demo-server -- This is a simple "Hello, World" WebRTC data channel demonstration. This web server communicates with clients via WebSocket, and maintains a roster of connected clients. Use the demo branch.
3. webrtc-sctp -- This is the SCTP implementation which is being demonstrated. Use the demo branch.

Set up the repositories:

$ mkdir work
$ cd work
$ git clone https://github.com/simmons/webrtc-demo-client.git
$ git clone https://github.com/simmons/webrtc-demo-server.git
$ git clone https://github.com/simmons/webrtc-sctp.git
$ ( cd webrtc-demo-server && git checkout demo )
$ ( cd webrtc-sctp && git checkout demo )

Run the server:

$ cd webrtc-demo-server
$ cargo run

Go to http://localhost:8080/ in your web browser. (I've tested Chrome and Firefox.) You should see the roster with only your web browser listed.

From another terminal, run the client:

$ cd webrtc-demo-client
$ cargo run

You should see the Rust client now listed in the roster, with a "Chat" button. Click the Chat button to start the WebRTC data channel.

License

This crate is distributed under the terms of both the MIT license and the Apache License (Version 2.0). See LICENSE-MIT and LICENSE-APACHE for details.

Contributing

Unless you explicitly state otherwise, any contribution you intentionally submit for inclusion in the work, as defined in the Apache-2.0 license, shall be dual-licensed as above, without any additional terms or conditions.