socket.io/examples/nuxt-example/server/plugins/socket.io.ts

import type { NitroApp } from "nitropack";
import { Server as Engine } from "engine.io";
import { Server } from "socket.io";
import { defineEventHandler } from "h3";

export default defineNitroPlugin((nitroApp: NitroApp) => {
  const engine = new Engine();
  const io = new Server();

  io.bind(engine);

  io.on("connection", (socket) => {
    // ...
  });

  nitroApp.router.use("/socket.io/", defineEventHandler({
    handler(event) {
      engine.handleRequest(event.node.req, event.node.res);
      event._handled = true;
    },
    websocket: {
      open(peer) {
        // crossws >= 0.3.0
        // @ts-expect-error private method and property
        engine.prepare(peer._internal.nodeReq);
        // @ts-expect-error private method and property
        engine.onWebSocket(peer._internal.nodeReq, peer._internal.nodeReq.socket, peer.websocket);

        // crossws < 0.3.0
        // const context = peer.ctx.node;
        // // @ts-expect-error private method
        // engine.prepare(context.req);
        // // @ts-expect-error private method
        // engine.onWebSocket(context.req, context.req.socket, context.ws);
      }
    }
  }));
});