Nitro

import { defineConfig } from "nitro";

export default defineConfig({
  features: { websocket: true },
});

import { defineWebSocketHandler } from "nitro";

export default defineWebSocketHandler({
  open(peer) {
    console.log("connected", peer.id);
    peer.send("Welcome!");
  },
  message(peer, message) {
    peer.send(`echo: ${message.text()}`);
  },
  close(peer, details) {
    console.log("closed", details.code, details.reason);
  },
  error(peer, error) {
    console.error(error);
  },
});

import { defineWebSocketHandler } from "nitro";

export default defineWebSocketHandler({
  upgrade(request) {
    const token = new URL(request.url).searchParams.get("token");
    if (!isValid(token)) throw new Response("Unauthorized", { status: 401 });
    return { context: { userId: getUserId(token) } }; // also: headers, protocol, namespace, handled
  },
  open(peer) {
    console.log("user", peer.context.userId);
  },
});

peer.send("text");                 // or an object -> JSON
peer.subscribe("topic");
peer.unsubscribe("topic");
peer.publish("topic", data);       // broadcast to subscribers (not the sender)
peer.close(1000, "bye");
peer.terminate();

import { defineWebSocketHandler } from "nitro";

export default defineWebSocketHandler({
  open(peer) {
    peer.subscribe("messages");
    peer.publish("messages", `${peer} joined ${peer.namespace}`);
  },
  message(peer, message) {
    peer.publish("messages", `${peer}: ${message.text()}`); // only same namespace
  },
  close(peer) {
    peer.publish("messages", `${peer} left`);
  },
});

import { defineHandler } from "nitro";
import { createEventStream } from "nitro/h3";

export default defineHandler((event) => {
  const stream = createEventStream(event);
  const interval = setInterval(() => {
    stream.push(`tick @ ${Date.now()}`);
  }, 1000);
  stream.onClosed(() => clearInterval(interval));
  return stream.send();
});