MPyC Web

MPyC Web is a port of the MPyC Python framework for Web Browsers. It uses:

• PyScript for running Python code in the browser via WebAssembly
• PeerJS for peer-to-peer connections via WebRTC

Demo deployments

• Demo (stable):
  • GitHub Pages - https://e-nikolov.github.io/mpyc-web
  • Netlify - https://mpyc-web.netlify.app
• Demo (test):
  • GitHub Pages - https://e-nikolov.github.io/mpyc-test
  • Netlify - https://mpyc-test.netlify.app
• Starter:
  • GitHub Pages - https://e-nikolov.github.io/mpyc-web-starter
  • Netlify - https://mpyc-web-starter.netlify.app

Examples

• Starter - https://github.com/e-nikolov/mpyc-web/tree/master/mpyc-web-starter/index.html
• Starter Standalone - https://github.com/e-nikolov/mpyc-web-starter
• Demo - https://github.com/e-nikolov/mpyc-web/tree/master/mpyc-web-demo

Usage

Import

import { MPCManager, PeerJSTransport, PyScriptWorkerRuntime } from 'https://cdn.jsdelivr.net/npm/@mpyc-web/core/+esm';

Create an MPCManager

The MPCManager requires a transport and a runtime:

let mpyc = new MPCManager(
   () => new PeerJSTransport(),
   () => new PyScriptWorkerRuntime()
);

Handle runtime output events

// Triggered when the mpc runtime writes to stdout:
mpyc.on("runtime:display", async (message) => {
   // Do something with the message, e.g. write it to a xterm.js terminal
})

// Triggered when the mpc runtime writes to stderr:
mpyc.on("runtime:display:error", async (error) => {
   // Do something with the error, e.g. write it to a xterm.js terminal
})

Handle transport events

// Triggered when the transport is ready and has an ID
mpyc.on("transport:ready", async (partyID) => {
   // Do something with our ID, e.g. send it to someone else via a chat message so they can connect to us
})

// Triggered when someone has connected to us
mpyc.on("transport:conn:ready", async (peerID) => {
   // Do something with their ID
});

// Triggered when someone has disconnected from us
mpyc.on("transport:conn:disconnected", async (peerID) => {
   // Do something with their ID
});

Connect to another party via their ID

mpyc.transport.connect("<the other party's ID>")

Execute an MPC with the connected parties

mpyc.runMPC('<Python source code using the MPyC framework>', '<filename to be shown in debug outputs>');

Notes

mpyc-web relies on some relatively new browser features:

• WebAssembly
• WebRTC
• WebWorkers
• Atomics
• SharedArrayBuffer

Some of those features only work in secure contexts, which requires some additional headers to be specified by the server:

Cross-Origin-Opener-Policy: same-origin
Cross-Origin-Embedder-Policy: require-corp

If it is not possible to configure the server to supply those headers, e.g. on GitHub Pages, an alternative is to use a ServiceWorker to intercept the responses and add the necessary headers, see coi-serviceworker. This solution however does not work in some cases, e.g. a private window on Firefox.

Development

Dependencies

1. Install nix
   1. Linux with Systemd or MacOS - https://github.com/DeterminateSystems/nix-installer/
   2. Linux without Systemd - https://nixos.org/download.html
2. Start a development shell with all necessary tools - nix develop --impure
3. Install the JavaScript dependencies - yarn install

Start a development server

yarn dev

Build as a static site

yarn build

Run the static site

python -m http.server -d dist