✉️ WebSockets

• WebSockets Reference
• Using WebSockets

Server

Miniflare will always upgrade Web Socket connections. The Worker must respond with a status 101 Switching Protocols response including a webSocket. For example, the Worker below implements an echo WebSocket server:

export default {
  fetch(request) {
    const [client, server] = Object.values(new WebSocketPair());

    server.accept();
    server.addEventListener("message", (event) => {
      server.send(event.data);
    });

    return new Response(null, {
      status: 101,
      webSocket: client,
    });
  },
};

When using dispatchFetch, you are responsible for handling WebSockets by using the webSocket property on Response. As an example, if the above worker script was stored in echo.mjs:

import { Miniflare } from "miniflare";

const mf = new Miniflare({
  modules: true,
  scriptPath: "echo.mjs",
});

const res = await mf.dispatchFetch("https://example.com", {
  headers: {
    Upgrade: "websocket",
  },
});
const webSocket = res.webSocket;
webSocket.accept();
webSocket.addEventListener("message", (event) => {
  console.log(event.data);
});

webSocket.send("Hello!"); // Above listener logs "Hello!"