chore(release): @socket.io/redis-streams-emitter@0.1.0

Related: https://github.com/socketio/socket.io-redis-streams-adapter/issues/8

CHANGELOG.md

@@ -10,6 +10,7 @@ Here are the detailed changelogs for each package in this monorepo:
 | `socket.io`                    | [link](packages/socket.io/CHANGELOG.md)                 |
 | `socket.io-adapter`            | [link](packages/socket.io-adapter/CHANGELOG.md)         |
 | `socket.io-client`             | [link](packages/socket.io-client/CHANGELOG.md)          |
+| `@socket.io/cluster-adapter`   | [link](packages/socket.io-cluster-adapter/CHANGELOG.md) |
 | `@socket.io/cluster-engine`    | [link](packages/socket.io-cluster-engine/CHANGELOG.md)  |
 | `@socket.io/component-emitter` | [link](packages/socket.io-component-emitter/History.md) |
 | `socket.io-parser`             | [link](packages/socket.io-parser/CHANGELOG.md)          |

examples/basic-websocket-client/package.json

@@ -7,7 +7,7 @@
     "prettier": "^2.8.4",
     "rollup": "^3.20.2",
     "socket.io": "^4.6.1",
-    "ws": "^8.13.0"
+    "ws": "^8.18.3"
   },
   "scripts": {
     "bundle": "rollup -c",

package.json

@@ -8,15 +8,17 @@
     "packages/socket.io-cluster-engine",
     "packages/engine.io-client",
     "packages/socket.io-adapter",
+    "packages/socket.io-cluster-adapter",
     "packages/socket.io-parser",
     "packages/socket.io-client",
     "packages/socket.io",
-    "packages/socket.io-postgres-emitter"
+    "packages/socket.io-postgres-emitter",
+    "packages/socket.io-redis-streams-emitter"
   ],
   "overrides": {
     "@types/estree": "0.0.52",
     "@types/lodash": "4.14.189",
-    "ws": "8.17.1"
+    "ws": "8.18.3"
   },
   "devDependencies": {
     "@babel/core": "^7.24.7",
@@ -31,6 +33,7 @@
     "@rollup/plugin-node-resolve": "^15.2.3",
     "@sinonjs/fake-timers": "^11.2.2",
     "@socket.io/postgres-adapter": "^0.1.0",
+    "@socket.io/redis-streams-adapter": "~0.2.2",
     "@types/debug": "^4.1.12",
     "@types/expect.js": "^0.3.32",
     "@types/mocha": "^10.0.7",
@@ -73,6 +76,7 @@
     "ts-loader": "^9.5.1",
     "ts-node": "^10.9.2",
     "tsd": "^0.31.1",
+    "tsx": "~4.20.6",
     "typescript": "^5.5.3",
     "uWebSockets.js": "github:uNetworking/uWebSockets.js#v20.48.0",
     "wdio-geckodriver-service": "^5.0.2"

packages/engine.io-client/lib/transport.ts

@@ -192,7 +192,7 @@ export abstract class Transport extends Emitter<
   private _port() {
     if (
       this.opts.port &&
-      ((this.opts.secure && Number(this.opts.port !== 443)) ||
+      ((this.opts.secure && Number(this.opts.port) !== 443) ||
         (!this.opts.secure && Number(this.opts.port) !== 80))
     ) {
       return ":" + this.opts.port;

packages/engine.io-client/package.json

@@ -53,9 +53,9 @@
   ],
   "dependencies": {
     "@socket.io/component-emitter": "~3.1.0",
-    "debug": "~4.3.1",
+    "debug": "~4.4.1",
     "engine.io-parser": "~5.2.1",
-    "ws": "~8.17.1",
+    "ws": "~8.18.3",
     "xmlhttprequest-ssl": "~2.1.1"
   },
   "scripts": {

packages/engine.io-client/test/transport.js

@@ -116,6 +116,32 @@ describe("Transport", () => {
       expect(polling.uri()).to.contain("https://localhost/engine.io?sid=test");
     });
 
+    it("should generate an https uri w/o a port (string)", () => {
+      const polling = new eio.transports.polling({
+        path: "/engine.io",
+        hostname: "localhost",
+        secure: true,
+        query: { sid: "test" },
+        port: "443",
+        timestampRequests: false,
+      });
+      expect(polling.uri()).to.contain("https://localhost/engine.io?sid=test");
+    });
+
+    it("should generate an https uri with a port", () => {
+      const polling = new eio.transports.polling({
+        path: "/engine.io",
+        hostname: "localhost",
+        secure: true,
+        query: { sid: "test" },
+        port: 8443,
+        timestampRequests: false,
+      });
+      expect(polling.uri()).to.contain(
+        "https://localhost:8443/engine.io?sid=test",
+      );
+    });
+
     it("should generate a timestamped uri", () => {
       const polling = new eio.transports.polling({
         path: "/engine.io",

packages/engine.io/package.json

@@ -37,9 +37,9 @@
     "base64id": "2.0.0",
     "cookie": "~0.7.2",
     "cors": "~2.8.5",
-    "debug": "~4.3.1",
+    "debug": "~4.4.1",
     "engine.io-parser": "~5.2.1",
-    "ws": "~8.17.1"
+    "ws": "~8.18.3"
   },
   "scripts": {
     "compile": "rimraf ./build && tsc",

packages/socket.io-adapter/lib/cluster-adapter.ts

@@ -199,6 +199,14 @@ export abstract class ClusterAdapter extends Adapter {
       return debug("[%s] ignore message from self", this.uid);
     }
 
+    if (message.nsp !== this.nsp.name) {
+      return debug(
+        "[%s] ignore message from another namespace (%s)",
+        this.uid,
+        message.nsp,
+      );
+    }
+
     debug(
       "[%s] new event of type %d from %s",
       this.uid,
@@ -671,6 +679,8 @@ export abstract class ClusterAdapter extends Adapter {
   protected publish(
     message: DistributiveOmit<ClusterMessage, "nsp" | "uid">,
   ): void {
+    debug("[%s] sending message %s", this.uid, message.type);
+
     this.publishAndReturnOffset(message).catch((err) => {
       debug("[%s] error while publishing message: %s", this.uid, err);
     });
@@ -699,6 +709,14 @@ export abstract class ClusterAdapter extends Adapter {
   ) {
     (response as ClusterResponse).uid = this.uid;
     (response as ClusterResponse).nsp = this.nsp.name;
+
+    debug(
+      "[%s] sending response %s to %s",
+      this.uid,
+      response.type,
+      requesterUid,
+    );
+
     this.doPublishResponse(requesterUid, response as ClusterResponse).catch(
       (err) => {
         debug("[%s] error while publishing response: %s", this.uid, err);
@@ -790,17 +808,10 @@ export abstract class ClusterAdapterWithHeartbeat extends ClusterAdapter {
     }
 
     if (message.uid && message.uid !== EMITTER_UID) {
-      // we track the UID of each sender, in order to know how many servers there are in the cluster
+      // we track the UID of each sender to know how many servers there are in the cluster
       this.nodesMap.set(message.uid, Date.now());
     }
 
-    debug(
-      "[%s] new event of type %d from %s",
-      this.uid,
-      message.type,
-      message.uid,
-    );
-
     switch (message.type) {
       case MessageType.INITIAL_HEARTBEAT:
         this.publish({

packages/socket.io-adapter/package.json

@@ -17,8 +17,8 @@
   "types": "./dist/index.d.ts",
   "description": "default socket.io in-memory adapter",
   "dependencies": {
-    "debug": "~4.3.4",
-    "ws": "~8.17.1"
+    "debug": "~4.4.1",
+    "ws": "~8.18.3"
   },
   "scripts": {
     "compile": "rimraf ./dist && tsc",

packages/socket.io-adapter/test/cluster-adapter.ts

@@ -67,11 +67,6 @@ describe("cluster adapter", () => {
           serverSockets.push(socket);
           servers.push(io);
           if (servers.length === NODES_COUNT) {
-            // ensure all nodes know each other
-            servers[0].emit("ping");
-            servers[1].emit("ping");
-            servers[2].emit("ping");
-
             done();
           }
         });

packages/socket.io-client/package.json

@@ -46,7 +46,7 @@
   "types": "./build/esm/index.d.ts",
   "dependencies": {
     "@socket.io/component-emitter": "~3.1.0",
-    "debug": "~4.3.2",
+    "debug": "~4.4.1",
     "engine.io-client": "~6.6.1",
     "socket.io-parser": "~4.2.4"
   },

packages/socket.io-client/wdio.conf.js

@@ -60,7 +60,7 @@ if (process.env.CI === "true") {
     {
       browserName: "internet explorer",
       browserVersion: "10",
-      platformName: "Windows 7",
+      platformName: "Windows 8",
       "sauce:options": BASE_SAUCE_OPTIONS,
     },
     {

packages/socket.io-cluster-adapter/CHANGELOG.md

@@ -0,0 +1,60 @@
+# Changelog
+
+| Version                  | Release date |
+|--------------------------|--------------|
+| [0.3.0](#030-2025-10-16) | October 2025 |
+| [0.2.2](#022-2023-03-24) | March 2023   |
+| [0.2.1](#021-2022-10-13) | October 2022 |
+| [0.2.0](#020-2022-04-28) | April 2022   |
+| [0.1.0](#010-2021-06-22) | June 2021    |
+
+
+
+## [0.3.0](https://github.com/socketio/socket.io-cluster-adapter/compare/0.2.2...0.3.0) (2025-10-16)
+
+This release contains an important refactor of the adapter ([this commit](https://github.com/socketio/socket.io-cluster-adapter/commit/0c431243e28913fdd2a4a3de3e67a9f38d67a3aa)), as most of the logic has been moved in the `ClusterAdapter` class of the `socket.io-adapter` package.
+
+Besides, the `@socket.io/cluster-adapter` package is now part of the `socket.io` monorepo.
+
+
+
+## [0.2.2](https://github.com/socketio/socket.io-cluster-adapter/compare/0.2.1...0.2.2) (2023-03-24)
+
+The `socket.io-adapter` package was added to the list of `peerDependencies`, in order to fix sync issues with the version imported by the socket.io package (see [15fd56e](https://github.com/socketio/socket.io-cluster-adapter/commit/15fd56e78d52aa65c5fbf412dec57ab4bdaee7cc)).
+
+Support for connection state recovery (see [here](https://github.com/socketio/socket.io/releases/4.6.0)) will be added in the next release.
+
+
+
+## [0.2.1](https://github.com/socketio/socket.io-cluster-adapter/compare/0.2.0...0.2.1) (2022-10-13)
+
+
+### Bug Fixes
+
+* properly handle ERR_IPC_CHANNEL_CLOSED errors ([#6](https://github.com/socketio/socket.io-cluster-adapter/issues/6)) ([be0a0e3](https://github.com/socketio/socket.io-cluster-adapter/commit/be0a0e3217bd7100d569e5624194612bcc8b96ff))
+
+
+
+## [0.2.0](https://github.com/socketio/socket.io-cluster-adapter/compare/0.1.0...0.2.0) (2022-04-28)
+
+
+### Features
+
+* broadcast and expect multiple acks ([055b784](https://github.com/socketio/socket.io-cluster-adapter/commit/055b7840d8cf88173d8299041ef3fafa9791c97a))
+
+This feature was added in `socket.io@4.5.0`:
+
+```js
+io.timeout(1000).emit("some-event", (err, responses) => {
+  // ...
+});
+```
+
+Thanks to this change, it will now work within a Node.js cluster.
+
+
+
+## 0.1.0 (2021-06-22)
+
+Initial commit
+

packages/socket.io-cluster-adapter/LICENSE

@@ -0,0 +1,7 @@
+Copyright (c) 2021 Damien Arrachequesne (@darrachequesne)
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

packages/socket.io-cluster-adapter/README.md

@@ -0,0 +1,100 @@
+# Socket.IO cluster adapter
+
+The `@socket.io/cluster-adapter` package allows broadcasting packets between multiple Socket.IO servers.
+
+![Adapter diagram](./assets/adapter.png)
+
+It can be used in conjunction with [`@socket.io/sticky`](https://github.com/socketio/socket.io-sticky) to broadcast packets between the workers of the same Node.js [cluster](https://nodejs.org/api/cluster.html).
+
+Supported features:
+
+- [broadcasting](https://socket.io/docs/v4/broadcasting-events/)
+- [utility methods](https://socket.io/docs/v4/server-instance/#Utility-methods)
+  - [`socketsJoin`](https://socket.io/docs/v4/server-instance/#socketsJoin)
+  - [`socketsLeave`](https://socket.io/docs/v4/server-instance/#socketsLeave)
+  - [`disconnectSockets`](https://socket.io/docs/v4/server-instance/#disconnectSockets)
+  - [`fetchSockets`](https://socket.io/docs/v4/server-instance/#fetchSockets)
+  - [`serverSideEmit`](https://socket.io/docs/v4/server-instance/#serverSideEmit)
+
+Related packages:
+
+- Postgres adapter: https://github.com/socketio/socket.io-postgres-adapter/
+- Redis adapter: https://github.com/socketio/socket.io-redis-adapter/
+- MongoDB adapter: https://github.com/socketio/socket.io-mongo-adapter/
+
+**Table of contents**
+
+- [Installation](#installation)
+- [Usage](#usage)
+- [License](#license)
+
+## Installation
+
+```
+npm install @socket.io/cluster-adapter
+```
+
+## Usage
+
+```js
+const cluster = require("cluster");
+const http = require("http");
+const { Server } = require("socket.io");
+const numCPUs = require("os").cpus().length;
+const { setupMaster, setupWorker } = require("@socket.io/sticky");
+const { createAdapter, setupPrimary } = require("@socket.io/cluster-adapter");
+
+if (cluster.isMaster) {
+  console.log(`Master ${process.pid} is running`);
+
+  const httpServer = http.createServer();
+
+  // setup sticky sessions
+  setupMaster(httpServer, {
+    loadBalancingMethod: "least-connection",
+  });
+
+  // setup connections between the workers
+  setupPrimary();
+
+  // needed for packets containing buffers (you can ignore it if you only send plaintext objects)
+  // Node.js < 16.0.0
+  cluster.setupMaster({
+    serialization: "advanced",
+  });
+  // Node.js > 16.0.0
+  // cluster.setupPrimary({
+  //   serialization: "advanced",
+  // });
+
+  httpServer.listen(3000);
+
+  for (let i = 0; i < numCPUs; i++) {
+    cluster.fork();
+  }
+
+  cluster.on("exit", (worker) => {
+    console.log(`Worker ${worker.process.pid} died`);
+    cluster.fork();
+  });
+} else {
+  console.log(`Worker ${process.pid} started`);
+
+  const httpServer = http.createServer();
+  const io = new Server(httpServer);
+
+  // use the cluster adapter
+  io.adapter(createAdapter());
+
+  // setup connection with the primary process
+  setupWorker(io);
+
+  io.on("connection", (socket) => {
+    /* ... */
+  });
+}
+```
+
+## License
+
+[MIT](LICENSE)

packages/socket.io-cluster-adapter/assets/adapter.excalidraw

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packages/socket.io-cluster-adapter/lib/index.ts

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+import cluster from "node:cluster";
+import {
+  ClusterAdapterWithHeartbeat,
+  ClusterAdapterOptions,
+  ClusterMessage,
+  ServerId,
+  ClusterResponse,
+  MessageType,
+} from "socket.io-adapter";
+import debugModule from "debug";
+
+const debug = debugModule("socket.io-cluster-adapter");
+const MESSAGE_SOURCE = "_sio_adapter";
+const hasOwnProperty = Object.prototype.hasOwnProperty;
+
+function ignoreError() {}
+
+/**
+ * Returns a function that will create a NodeClusterAdapter instance.
+ *
+ * @param opts - additional options
+ *
+ * @public
+ * @see https://nodejs.org/api/cluster.html
+ */
+export function createAdapter(opts: Partial<ClusterAdapterOptions> = {}) {
+  return function (nsp: any) {
+    return new NodeClusterAdapter(nsp, opts);
+  };
+}
+
+export class NodeClusterAdapter extends ClusterAdapterWithHeartbeat {
+  constructor(nsp: any, opts: ClusterAdapterOptions = {}) {
+    super(nsp, opts);
+    process.on("message", (message: any) => {
+      const isValidSource = message?.source === MESSAGE_SOURCE;
+      if (!isValidSource) {
+        debug("[%s] ignore unknown source", this.uid);
+        return;
+      }
+
+      // note: this check should be done in the onMessage() handler
+      if (message.nsp !== this.nsp.name) {
+        debug("[%s] ignore other namespace", this.uid);
+        return;
+      }
+
+      this.onMessage(message);
+    });
+
+    // until https://github.com/socketio/socket.io/commit/f3e1f5ebdf59158d0c8d1e20f8230275617fb355 is released
+    this.init();
+  }
+
+  protected override doPublish(message: ClusterMessage & { source: string }) {
+    message.source = MESSAGE_SOURCE;
+
+    process.send(message, null, {}, ignoreError);
+
+    return Promise.resolve(""); // connection state recovery is not supported
+  }
+
+  protected override doPublishResponse(
+    requesterUid: ServerId,
+    response: ClusterResponse & { source: string; requesterUid: string },
+  ) {
+    response.source = MESSAGE_SOURCE;
+    response.requesterUid = requesterUid;
+
+    process.send(response, null, {}, ignoreError);
+
+    return Promise.resolve();
+  }
+}
+
+const UIDS = Symbol("uids");
+
+export function setupPrimary() {
+  cluster.on("message", (worker, message) => {
+    const isValidSource = message?.source === MESSAGE_SOURCE;
+    if (!isValidSource) {
+      return;
+    }
+
+    // store the requester's uids (one per namespace) so that the response can be sent specifically to them
+    worker[UIDS] = worker[UIDS] || new Set();
+    worker[UIDS].add(message.uid);
+
+    switch (message.type) {
+      case MessageType.FETCH_SOCKETS_RESPONSE:
+      case MessageType.SERVER_SIDE_EMIT_RESPONSE:
+        const requesterUid = message.requesterUid;
+        for (const workerId in cluster.workers) {
+          if (
+            hasOwnProperty.call(cluster.workers, workerId) &&
+            cluster.workers[workerId][UIDS]?.has(requesterUid)
+          ) {
+            cluster.workers[workerId].send(message, null, ignoreError);
+            break;
+          }
+        }
+        break;
+      default:
+        const emitterIdAsString = String(worker.id);
+        // emit to all workers but the requester
+        for (const workerId in cluster.workers) {
+          if (
+            hasOwnProperty.call(cluster.workers, workerId) &&
+            workerId !== emitterIdAsString
+          ) {
+            cluster.workers[workerId].send(message, null, ignoreError);
+          }
+        }
+    }
+  });
+}

packages/socket.io-cluster-adapter/package.json

@@ -0,0 +1,40 @@
+{
+  "name": "@socket.io/cluster-adapter",
+  "version": "0.3.0",
+  "description": "The Socket.IO cluster adapter, allowing to broadcast events between several Socket.IO servers",
+  "license": "MIT",
+  "homepage": "https://github.com/socketio/socket.io/tree/main/packages/socket.io-cluster-adapter#readme",
+  "repository": {
+    "type": "git",
+    "url": "git+https://github.com/socketio/socket.io.git"
+  },
+  "bugs": {
+    "url": "https://github.com/socketio/socket.io/issues"
+  },
+  "files": [
+    "dist/"
+  ],
+  "main": "./dist/index.js",
+  "types": "./dist/index.d.ts",
+  "scripts": {
+    "compile": "rimraf ./dist && tsc",
+    "test": "npm run format:check && npm run compile && nyc mocha --import=tsx test/index.ts",
+    "format:check": "prettier --check \"lib/**/*.ts\" \"test/**/*.ts\"",
+    "format:fix": "prettier --write \"lib/**/*.ts\" \"test/**/*.ts\"",
+    "prepack": "npm run compile"
+  },
+  "dependencies": {
+    "debug": "~4.4.1"
+  },
+  "peerDependencies": {
+    "socket.io-adapter": "~2.5.5"
+  },
+  "engines": {
+    "node": ">=10.0.0"
+  },
+  "keywords": [
+    "socket.io",
+    "cluster",
+    "adapter"
+  ]
+}

packages/socket.io-cluster-adapter/test/index.ts

@@ -0,0 +1,372 @@
+import { io as ioc, Socket as ClientSocket } from "socket.io-client";
+import expect = require("expect.js");
+import { setupPrimary } from "..";
+import { times, sleep } from "./util";
+import cluster, { Worker } from "node:cluster";
+
+const NODES_COUNT = 3;
+
+cluster.setupMaster({
+  exec: "./test/worker.js",
+  // @ts-ignore
+  serialization: "advanced", // needed for packets containing buffers
+});
+
+setupPrimary();
+
+const getRooms = (worker): Promise<Set<string>> => {
+  worker.send("get rooms");
+  return new Promise((resolve) => {
+    worker.once("message", (content) => {
+      resolve(content);
+    });
+  });
+};
+
+describe("@socket.io/cluster-adapter", () => {
+  let clientSockets: ClientSocket[], workers: Worker[];
+
+  beforeEach((done) => {
+    clientSockets = [];
+    workers = [];
+
+    for (let i = 1; i <= NODES_COUNT; i++) {
+      const PORT = 40000 + i;
+      const worker = cluster.fork({
+        PORT,
+      });
+
+      worker.on("listening", () => {
+        const clientSocket = ioc(`http://localhost:${PORT}`);
+
+        clientSocket.on("connect", async () => {
+          workers.push(worker);
+          clientSockets.push(clientSocket);
+          if (clientSockets.length === NODES_COUNT) {
+            done();
+          }
+        });
+      });
+    }
+  });
+
+  afterEach(() => {
+    for (const id in cluster.workers) {
+      cluster.workers[id].kill();
+    }
+    clientSockets.forEach((socket) => {
+      socket.disconnect();
+    });
+  });
+
+  describe("broadcast", function () {
+    it("broadcasts to all clients", (done) => {
+      const partialDone = times(3, done);
+
+      clientSockets.forEach((clientSocket) => {
+        clientSocket.on("test", (arg1, arg2, arg3) => {
+          expect(arg1).to.eql(1);
+          expect(arg2).to.eql("2");
+          expect(Buffer.isBuffer(arg3)).to.be(true);
+          partialDone();
+        });
+      });
+
+      workers[0].send("broadcasts to all clients");
+    });
+
+    it("broadcasts to all clients in a namespace", (done) => {
+      const partialDone = times(3, done);
+
+      const onConnect = times(3, async () => {
+        workers[0].send("broadcasts to all clients in a namespace");
+      });
+
+      clientSockets.forEach((clientSocket) => {
+        const socket = clientSocket.io.socket("/custom");
+        socket.on("connect", onConnect);
+        socket.on("test", () => {
+          socket.disconnect();
+          partialDone();
+        });
+      });
+    });
+
+    it("broadcasts to all clients in a room", (done) => {
+      workers[1].send("join room1");
+
+      clientSockets[0].on("test", () => {
+        done(new Error("should not happen"));
+      });
+
+      clientSockets[1].on("test", () => {
+        done();
+      });
+
+      clientSockets[2].on("test", () => {
+        done(new Error("should not happen"));
+      });
+
+      workers[0].send("broadcasts to all clients in a room");
+    });
+
+    it("broadcasts to all clients except in room", (done) => {
+      const partialDone = times(2, done);
+      workers[1].send("join room1");
+
+      clientSockets[0].on("test", () => {
+        partialDone();
+      });
+
+      clientSockets[1].on("test", () => {
+        done(new Error("should not happen"));
+      });
+
+      clientSockets[2].on("test", () => {
+        partialDone();
+      });
+
+      workers[0].send("broadcasts to all clients except in room");
+    });
+
+    it("broadcasts to local clients only", (done) => {
+      clientSockets[0].on("test", () => {
+        done();
+      });
+
+      clientSockets[1].on("test", () => {
+        done(new Error("should not happen"));
+      });
+
+      clientSockets[2].on("test", () => {
+        done(new Error("should not happen"));
+      });
+
+      workers[0].send("broadcasts to local clients only");
+    });
+
+    it("broadcasts with multiple acknowledgements", (done) => {
+      clientSockets[0].on("test", (cb) => {
+        cb(1);
+      });
+
+      clientSockets[1].on("test", (cb) => {
+        cb(2);
+      });
+
+      clientSockets[2].on("test", (cb) => {
+        cb(3);
+      });
+
+      workers[0].send("broadcasts with multiple acknowledgements");
+
+      workers[0].on("message", (result) => {
+        if (result === "ok") {
+          done();
+        }
+      });
+    });
+
+    it("broadcasts with multiple acknowledgements (binary content)", (done) => {
+      clientSockets[0].on("test", (cb) => {
+        cb(Buffer.from([1]));
+      });
+
+      clientSockets[1].on("test", (cb) => {
+        cb(Buffer.from([2]));
+      });
+
+      clientSockets[2].on("test", (cb) => {
+        cb(Buffer.from([3]));
+      });
+
+      workers[0].send(
+        "broadcasts with multiple acknowledgements (binary content)",
+      );
+
+      workers[0].on("message", (result) => {
+        if (result === "ok") {
+          done();
+        }
+      });
+    });
+
+    it("broadcasts with multiple acknowledgements (no client)", (done) => {
+      workers[0].send("broadcasts with multiple acknowledgements (no client)");
+
+      workers[0].on("message", (result) => {
+        if (result === "ok") {
+          done();
+        }
+      });
+    });
+
+    it("broadcasts with multiple acknowledgements (timeout)", (done) => {
+      clientSockets[0].on("test", (cb) => {
+        cb(1);
+      });
+
+      clientSockets[1].on("test", (cb) => {
+        cb(2);
+      });
+
+      clientSockets[2].on("test", (cb) => {
+        // do nothing
+      });
+
+      workers[0].send("broadcasts with multiple acknowledgements (timeout)");
+
+      workers[0].on("message", (result) => {
+        if (result === "ok") {
+          done();
+        }
+      });
+    });
+  });
+
+  describe("socketsJoin", () => {
+    it("makes all socket instances join the specified room", async () => {
+      workers[0].send("makes all socket instances join the specified room");
+
+      await sleep(100);
+
+      expect((await getRooms(workers[0])).has("room1")).to.be(true);
+      expect((await getRooms(workers[1])).has("room1")).to.be(true);
+      expect((await getRooms(workers[2])).has("room1")).to.be(true);
+    });
+
+    it("makes the matching socket instances join the specified room", async () => {
+      workers[0].send("join room1");
+      workers[2].send("join room1");
+
+      workers[0].send(
+        "makes the matching socket instances join the specified room",
+      );
+
+      await sleep(100);
+
+      expect((await getRooms(workers[0])).has("room2")).to.be(true);
+      expect((await getRooms(workers[1])).has("room2")).to.be(false);
+      expect((await getRooms(workers[2])).has("room2")).to.be(true);
+    });
+  });
+
+  describe("socketsLeave", () => {
+    it("makes all socket instances leave the specified room", async () => {
+      workers[0].send("join room1");
+      workers[2].send("join room1");
+
+      workers[0].send("makes all socket instances leave the specified room");
+
+      await sleep(100);
+
+      expect((await getRooms(workers[0])).has("room1")).to.be(false);
+      expect((await getRooms(workers[1])).has("room1")).to.be(false);
+      expect((await getRooms(workers[2])).has("room1")).to.be(false);
+    });
+
+    it("makes the matching socket instances leave the specified room", async () => {
+      workers[0].send("join room1 & room2");
+      workers[2].send("join room2");
+
+      workers[0].send(
+        "makes the matching socket instances leave the specified room",
+      );
+
+      await sleep(100);
+
+      expect((await getRooms(workers[0])).has("room2")).to.be(false);
+      expect((await getRooms(workers[1])).has("room2")).to.be(false);
+      expect((await getRooms(workers[2])).has("room2")).to.be(true);
+    });
+  });
+
+  describe("disconnectSockets", () => {
+    it("makes all socket instances disconnect", (done) => {
+      const partialDone = times(3, done);
+
+      clientSockets.forEach((clientSocket) => {
+        clientSocket.on("disconnect", (reason) => {
+          expect(reason).to.eql("io server disconnect");
+          partialDone();
+        });
+      });
+
+      workers[0].send("makes all socket instances disconnect");
+    });
+  });
+
+  describe("fetchSockets", () => {
+    it("returns all socket instances", (done) => {
+      workers[0].send("returns all socket instances");
+
+      workers[0].on("message", (result) => {
+        if (result === "ok") {
+          done();
+        }
+      });
+    });
+  });
+
+  describe("serverSideEmit", () => {
+    it("sends an event to other server instances", (done) => {
+      const partialDone = times(2, done);
+
+      workers[0].send("sends an event to other server instances");
+
+      workers[0].on("message", (result) => {
+        if (result === "ok") {
+          done(new Error("should not happen"));
+        }
+      });
+
+      workers[1].on("message", (result) => {
+        expect(result).to.eql("ok");
+        partialDone();
+      });
+
+      workers[2].on("message", (result) => {
+        expect(result).to.eql("ok");
+        partialDone();
+      });
+    });
+
+    it("sends an event and receives a response from the other server instances", (done) => {
+      workers[0].send(
+        "sends an event and receives a response from the other server instances (1)",
+      );
+      workers[1].send(
+        "sends an event and receives a response from the other server instances (2)",
+      );
+      workers[2].send(
+        "sends an event and receives a response from the other server instances (3)",
+      );
+
+      workers[0].on("message", (result) => {
+        if (result === "ok") {
+          done();
+        }
+      });
+    });
+
+    it("sends an event but timeout if one server does not respond", function (done) {
+      this.timeout(6000); // currently not possible to configure the timeout delay
+
+      workers[0].send(
+        "sends an event but timeout if one server does not respond (1)",
+      );
+      workers[1].send(
+        "sends an event but timeout if one server does not respond (2)",
+      );
+      workers[2].send(
+        "sends an event but timeout if one server does not respond (3)",
+      );
+
+      workers[0].on("message", (result) => {
+        if (result === "ok") {
+          done();
+        }
+      });
+    });
+  });
+});

packages/socket.io-cluster-adapter/test/util.ts

@@ -0,0 +1,13 @@
+export function times(count: number, fn: () => void) {
+  let i = 0;
+  return () => {
+    i++;
+    if (i === count) {
+      fn();
+    }
+  };
+}
+
+export function sleep(duration: number) {
+  return new Promise((resolve) => setTimeout(resolve, duration));
+}

packages/socket.io-cluster-adapter/test/worker.js

@@ -0,0 +1,182 @@
+const { createServer } = require("http");
+const { Server } = require("socket.io");
+const { createAdapter } = require("..");
+
+const httpServer = createServer();
+const io = new Server(httpServer);
+const expect = require("expect.js");
+
+io.adapter(createAdapter());
+
+let serverSocket;
+
+io.on("connection", (socket) => {
+  serverSocket = socket;
+});
+
+const customNamespace = io.of("/custom");
+
+process.on("message", async (msg) => {
+  switch (msg) {
+    case "broadcasts to all clients":
+      io.emit("test", 1, "2", Buffer.from([3, 4]));
+      break;
+    case "broadcasts to all clients in a namespace":
+      customNamespace.emit("test");
+      break;
+    case "join room1":
+      serverSocket.join("room1");
+      break;
+    case "join room1 & room2":
+      serverSocket.join(["room1", "room2"]);
+      break;
+    case "join room2":
+      serverSocket.join("room2");
+      break;
+    case "broadcasts to all clients in a room":
+      io.to("room1").emit("test");
+      break;
+    case "broadcasts to all clients except in room":
+      io.of("/").except("room1").emit("test");
+      break;
+    case "broadcasts to local clients only":
+      io.local.emit("test");
+      break;
+
+    case "broadcasts with multiple acknowledgements": {
+      io.timeout(500).emit("test", (err, responses) => {
+        expect(err).to.be(null);
+        expect(responses).to.contain(1);
+        expect(responses).to.contain(2);
+        expect(responses).to.contain(3);
+
+        setTimeout(() => {
+          expect(io.of("/").adapter.ackRequests.size).to.eql(0);
+
+          process.send("ok");
+        }, 500);
+      });
+      break;
+    }
+
+    case "broadcasts with multiple acknowledgements (binary content)": {
+      io.timeout(500).emit("test", (err, responses) => {
+        expect(err).to.be(null);
+        responses.forEach((response) => {
+          expect(Buffer.isBuffer(response)).to.be(true);
+        });
+
+        process.send("ok");
+      });
+      break;
+    }
+
+    case "broadcasts with multiple acknowledgements (no client)": {
+      io
+        .to("abc")
+        .timeout(500)
+        .emit("test", (err, responses) => {
+          expect(err).to.be(null);
+          expect(responses).to.eql([]);
+
+          process.send("ok");
+        });
+      break;
+    }
+
+    case "broadcasts with multiple acknowledgements (timeout)": {
+      io.timeout(500).emit("test", (err, responses) => {
+        expect(err).to.be.an(Error);
+        expect(responses).to.contain(1);
+        expect(responses).to.contain(2);
+
+        process.send("ok");
+      });
+      break;
+    }
+
+    case "get rooms":
+      process.send(serverSocket.rooms);
+      break;
+    case "makes all socket instances join the specified room":
+      io.socketsJoin("room1");
+      break;
+
+    case "makes the matching socket instances join the specified room":
+      io.in("room1").socketsJoin("room2");
+      break;
+
+    case "makes all socket instances leave the specified room":
+      io.socketsLeave("room1");
+      break;
+    case "makes the matching socket instances leave the specified room":
+      io.in("room1").socketsLeave("room2");
+      break;
+
+    case "makes all socket instances disconnect":
+      io.disconnectSockets();
+      break;
+
+    case "returns all socket instances":
+      const sockets = await io.fetchSockets();
+
+      expect(sockets).to.be.an(Array);
+      expect(sockets).to.have.length(3);
+      expect(io.of("/").adapter.requests.size).to.eql(0); // clean up
+
+      process.send("ok");
+      break;
+
+    case "sends an event to other server instances":
+      io.serverSideEmit("hello", "world", 1, "2");
+      break;
+    case "sends an event and receives a response from the other server instances (1)":
+      io.serverSideEmit("hello with ack", (err, response) => {
+        expect(err).to.be(null);
+        expect(response).to.be.an(Array);
+        expect(response).to.contain(2);
+        expect(response).to.contain("3");
+        process.send("ok");
+      });
+      break;
+    case "sends an event and receives a response from the other server instances (2)":
+      io.on("hello with ack", (cb) => {
+        cb(2);
+      });
+      break;
+    case "sends an event and receives a response from the other server instances (3)":
+      io.on("hello with ack", (cb) => {
+        cb("3");
+      });
+      break;
+    case "sends an event but timeout if one server does not respond (1)":
+      io.serverSideEmit("hello with ack", (err, response) => {
+        expect(err.message).to.be(
+          "timeout reached: missing 1 responses"
+        );
+        expect(response).to.be.an(Array);
+        expect(response).to.contain(2);
+        process.send("ok");
+      });
+      break;
+    case "sends an event but timeout if one server does not respond (2)":
+      io.on("hello with ack", (cb) => {
+        cb(2);
+      });
+      break;
+    case "sends an event but timeout if one server does not respond (3)":
+      io.on("hello with ack", (cb) => {
+        // do nothing
+      });
+      break;
+  }
+});
+
+io.on("hello", (arg1, arg2, arg3) => {
+  expect(arg1).to.eql("world");
+  expect(arg2).to.eql(1);
+  expect(arg3).to.eql("2");
+  process.send("ok");
+});
+
+httpServer.listen(parseInt(process.env.PORT, 10));

packages/socket.io-cluster-adapter/tsconfig.json

@@ -0,0 +1,13 @@
+{
+  "compilerOptions": {
+    "outDir": "./dist",
+    "allowJs": false,
+    "target": "es2017",
+    "module": "commonjs",
+    "declaration": true,
+    "esModuleInterop": true
+  },
+  "include": [
+    "./lib/**/*"
+  ]
+}

packages/socket.io-cluster-engine/package.json

@@ -19,7 +19,7 @@
   ],
   "dependencies": {
     "@msgpack/msgpack": "~2.8.0",
-    "debug": "~4.3.3",
+    "debug": "~4.4.1",
     "engine.io": "~6.6.0",
     "engine.io-parser": "~5.2.3"
   },

packages/socket.io-parser/package.json

@@ -26,7 +26,7 @@
   },
   "dependencies": {
     "@socket.io/component-emitter": "~3.1.0",
-    "debug": "~4.3.1"
+    "debug": "~4.4.1"
   },
   "scripts": {
     "compile": "rimraf ./build && tsc && tsc -p tsconfig.esm.json && ./postcompile.sh",

packages/socket.io-parser/wdio.conf.js

@@ -53,7 +53,7 @@ if (process.env.CI === "true") {
     {
       browserName: "internet explorer",
       browserVersion: "10",
-      platformName: "Windows 7",
+      platformName: "Windows 8",
       "sauce:options": BASE_SAUCE_OPTIONS,
     },
     {

packages/socket.io-postgres-emitter/package.json

@@ -22,7 +22,7 @@
   },
   "dependencies": {
     "@msgpack/msgpack": "^2.7.0",
-    "debug": "~4.3.1"
+    "debug": "~4.4.1"
   },
   "keywords": [
     "socket.io",

packages/socket.io-redis-streams-emitter/CHANGELOG.md

@@ -0,0 +1,9 @@
+# Changelog
+
+| Version                  | Release date  |
+|--------------------------|---------------|
+| [0.1.0](#010-2025-11-06) | November 2025 |
+
+## 0.1.0 (2025-11-06)
+
+Initial release!

packages/socket.io-redis-streams-emitter/LICENSE

@@ -0,0 +1,7 @@
+Copyright (c) 2025-present Guillermo Rauch and Socket.IO contributors
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

packages/socket.io-redis-streams-emitter/README.md

@@ -0,0 +1,220 @@
+# Socket.IO Redis Streams emitter
+
+The `@socket.io/redis-streams-emitter` package allows you to easily communicate with a group of Socket.IO servers from another Node.js process (server-side).
+
+It must be used in conjunction with [`@socket.io/redis-streams-adapter`](https://github.com/socketio/socket.io-redis-streams-adapter).
+
+**Table of contents**
+
+<!-- TOC -->
+  * [Installation](#installation)
+  * [Usage](#usage)
+    * [With the `redis` package](#with-the-redis-package)
+    * [With the `redis` package and a Redis cluster](#with-the-redis-package-and-a-redis-cluster)
+    * [With the `ioredis` package](#with-the-ioredis-package)
+    * [With the `ioredis` package and a Redis cluster](#with-the-ioredis-package-and-a-redis-cluster)
+  * [Options](#options)
+  * [API](#api)
+    * [`Emitter(redisClient[, nsp][, opts])`](#emitterredisclient-nsp-opts)
+    * [`Emitter#to(room:string):BroadcastOperator`](#emittertoroomstringbroadcastoperator)
+    * [`Emitter#in(room:string):BroadcastOperator`](#emitterinroomstringbroadcastoperator)
+    * [`Emitter#except(room:string):BroadcastOperator`](#emitterexceptroomstringbroadcastoperator)
+    * [`Emitter#of(namespace:string):Emitter`](#emitterofnamespacestringemitter)
+    * [`Emitter#socketsJoin(rooms:string|string[])`](#emittersocketsjoinroomsstringstring)
+    * [`Emitter#socketsLeave(rooms:string|string[])`](#emittersocketsleaveroomsstringstring)
+    * [`Emitter#disconnectSockets(close:boolean)`](#emitterdisconnectsocketscloseboolean)
+    * [`Emitter#serverSideEmit(ev:string[,...args:any[]])`](#emitterserversideemitevstringargsany)
+  * [License](#license)
+<!-- TOC -->
+
+## Installation
+
+```
+npm install @socket.io/redis-streams-emitter redis
+```
+
+## Usage
+
+### With the `redis` package
+
+```js
+import { createClient } from "redis";
+import { Emitter } from "@socket.io/redis-streams-emitter";
+
+const redisClient = createClient({
+  url: "redis://localhost:6379"
+});
+
+await redisClient.connect();
+
+const io = new Emitter(redisClient);
+
+setInterval(() => {
+  io.emit("ping", new Date());
+}, 1000);
+```
+
+### With the `redis` package and a Redis cluster
+
+```js
+import { createCluster } from "redis";
+import { Emitter } from "@socket.io/redis-streams-emitter";
+
+const redisClient = createCluster({
+  rootNodes: [
+    {
+      url: "redis://localhost:7000",
+    },
+    {
+      url: "redis://localhost:7001",
+    },
+    {
+      url: "redis://localhost:7002",
+    },
+  ],
+});
+
+await redisClient.connect();
+
+const io = new Emitter(redisClient);
+
+setInterval(() => {
+  io.emit("ping", new Date());
+}, 1000);
+```
+
+### With the `ioredis` package
+
+```js
+import { Redis } from "ioredis";
+import { Emitter } from "@socket.io/redis-streams-emitter";
+
+const redisClient = new Redis();
+
+const io = new Emitter(redisClient);
+
+setInterval(() => {
+  io.emit("ping", new Date());
+}, 1000);
+```
+
+### With the `ioredis` package and a Redis cluster
+
+```js
+import { Cluster } from "ioredis";
+import { Emitter } from "@socket.io/redis-streams-emitter";
+
+const redisClient = new Cluster([
+  {
+    host: "localhost",
+    port: 7000,
+  },
+  {
+    host: "localhost",
+    port: 7001,
+  },
+  {
+    host: "localhost",
+    port: 7002,
+  },
+]);
+
+const io = new Emitter(redisClient);
+
+setInterval(() => {
+  io.emit("ping", new Date());
+}, 1000);
+```
+
+## Options
+
+| Name         | Description                                                        | Default value |
+|--------------|--------------------------------------------------------------------|---------------|
+| `streamName` | The name of the Redis stream.                                      | `socket.io`   |
+| `maxLen`     | The maximum size of the stream. Almost exact trimming (~) is used. | `10_000`      |
+
+## API
+
+### `Emitter(redisClient[, nsp][, opts])`
+
+```js
+const io = new Emitter(redisClient);
+```
+
+### `Emitter#to(room:string):BroadcastOperator`
+### `Emitter#in(room:string):BroadcastOperator`
+
+Specifies a specific `room` that you want to emit to.
+
+```js
+io.to("room1").emit("hello");
+```
+
+### `Emitter#except(room:string):BroadcastOperator`
+
+Specifies a specific `room` that you want to exclude from broadcasting.
+
+```js
+io.except("room2").emit("hello");
+```
+
+### `Emitter#of(namespace:string):Emitter`
+
+Specifies a specific namespace that you want to emit to.
+
+```js
+const customNamespace = io.of("/custom");
+
+customNamespace.emit("hello");
+```
+
+### `Emitter#socketsJoin(rooms:string|string[])`
+
+Makes the matching socket instances join the specified rooms:
+
+```js
+// make all Socket instances join the "room1" room
+io.socketsJoin("room1");
+
+// make all Socket instances of the "admin" namespace in the "room1" room join the "room2" room
+io.of("/admin").in("room1").socketsJoin("room2");
+```
+
+### `Emitter#socketsLeave(rooms:string|string[])`
+
+Makes the matching socket instances leave the specified rooms:
+
+```js
+// make all Socket instances leave the "room1" room
+io.socketsLeave("room1");
+
+// make all Socket instances of the "admin" namespace in the "room1" room leave the "room2" room
+io.of("/admin").in("room1").socketsLeave("room2");
+```
+
+### `Emitter#disconnectSockets(close:boolean)`
+
+Makes the matching socket instances disconnect:
+
+```js
+// make all Socket instances disconnect
+io.disconnectSockets();
+
+// make all Socket instances of the "admin" namespace in the "room1" room disconnect
+io.of("/admin").in("room1").disconnectSockets();
+
+// this also works with a single socket ID
+io.of("/admin").in(theSocketId).disconnectSockets();
+```
+
+### `Emitter#serverSideEmit(ev:string[,...args:any[]])`
+
+Emits an event that will be received by each Socket.IO server of the cluster.
+
+```js
+io.serverSideEmit("ping");
+```
+
+## License
+
+[MIT](./LICENSE)

packages/socket.io-redis-streams-emitter/compose.yaml

@@ -0,0 +1,15 @@
+services:
+  redis:
+    image: redis:5
+    ports:
+      - "6379:6379"
+
+  redis-cluster:
+    image: grokzen/redis-cluster:7.0.10
+    ports:
+      - "7000-7005:7000-7005"
+
+  valkey:
+    image: valkey/valkey:8
+    ports:
+      - "6389:6379"

packages/socket.io-redis-streams-emitter/lib/index.ts

@@ -0,0 +1,496 @@
+import debugModule from "debug";
+import type {
+  DefaultEventsMap,
+  EventNames,
+  EventParams,
+  EventsMap,
+  TypedEventBroadcaster,
+} from "./typed-events";
+import { encode } from "@msgpack/msgpack";
+import { hasBinary, XADD } from "./util";
+import { ClusterMessage, MessageType, BroadcastFlags } from "socket.io-adapter";
+
+const debug = debugModule("socket.io-redis-streams-emitter");
+const EMITTER_UID = "emitter";
+
+type DistributiveOmit<T, K extends keyof any> = T extends any
+  ? Omit<T, K>
+  : never;
+
+// TODO move to the socket.io-adapter package
+abstract class BaseEmitter<
+  EmitEvents extends EventsMap = DefaultEventsMap,
+  ServerSideEvents extends EventsMap = DefaultEventsMap,
+> {
+  protected abstract publish(
+    message: DistributiveOmit<ClusterMessage, "uid" | "nsp">,
+  ): void;
+
+  /**
+   * Emits to all clients.
+   *
+   * @return Always true
+   * @public
+   */
+  public emit<Ev extends EventNames<EmitEvents>>(
+    ev: Ev,
+    ...args: EventParams<EmitEvents, Ev>
+  ): true {
+    return this.newBroadcastOperator().emit(ev, ...args);
+  }
+
+  /**
+   * Targets a room when emitting.
+   *
+   * @param room
+   * @return BroadcastOperator
+   * @public
+   */
+  public to(
+    room: string | string[],
+  ): BroadcastOperator<EmitEvents, ServerSideEvents> {
+    return this.newBroadcastOperator().to(room);
+  }
+
+  /**
+   * Targets a room when emitting.
+   *
+   * @param room
+   * @return BroadcastOperator
+   * @public
+   */
+  public in(
+    room: string | string[],
+  ): BroadcastOperator<EmitEvents, ServerSideEvents> {
+    return this.newBroadcastOperator().in(room);
+  }
+
+  /**
+   * Excludes a room when emitting.
+   *
+   * @param room
+   * @return BroadcastOperator
+   * @public
+   */
+  public except(
+    room: string | string[],
+  ): BroadcastOperator<EmitEvents, ServerSideEvents> {
+    return this.newBroadcastOperator().except(room);
+  }
+
+  /**
+   * Sets a modifier for a subsequent event emission that the event data may be lost if the client is not ready to
+   * receive messages (because of network slowness or other issues, or because they’re connected through long polling
+   * and is in the middle of a request-response cycle).
+   *
+   * @return BroadcastOperator
+   * @public
+   */
+  public get volatile(): BroadcastOperator<EmitEvents, ServerSideEvents> {
+    return this.newBroadcastOperator().volatile;
+  }
+
+  /**
+   * Sets the compress flag.
+   *
+   * @param compress - if `true`, compresses the sending data
+   * @return BroadcastOperator
+   * @public
+   */
+  public compress(
+    compress: boolean,
+  ): BroadcastOperator<EmitEvents, ServerSideEvents> {
+    return this.newBroadcastOperator().compress(compress);
+  }
+
+  /**
+   * Makes the matching socket instances join the specified rooms
+   *
+   * @param rooms
+   * @public
+   */
+  public socketsJoin(rooms: string | string[]): void {
+    return this.newBroadcastOperator().socketsJoin(rooms);
+  }
+
+  /**
+   * Makes the matching socket instances leave the specified rooms
+   *
+   * @param rooms
+   * @public
+   */
+  public socketsLeave(rooms: string | string[]): void {
+    return this.newBroadcastOperator().socketsLeave(rooms);
+  }
+
+  /**
+   * Makes the matching socket instances disconnect
+   *
+   * @param close - whether to close the underlying connection
+   * @public
+   */
+  public disconnectSockets(close: boolean = false): void {
+    return this.newBroadcastOperator().disconnectSockets(close);
+  }
+
+  /**
+   * Send a packet to the Socket.IO servers in the cluster
+   *
+   * @param ev - the event name
+   * @param args - any number of serializable arguments
+   */
+  public serverSideEmit<Ev extends EventNames<ServerSideEvents>>(
+    ev: Ev,
+    ...args: EventParams<ServerSideEvents, Ev>
+  ): void {
+    return this.newBroadcastOperator().serverSideEmit(ev, ...args);
+  }
+
+  private newBroadcastOperator() {
+    return new BroadcastOperator<EmitEvents, ServerSideEvents>((msg) =>
+      this.publish(msg),
+    );
+  }
+}
+
+export const RESERVED_EVENTS: ReadonlySet<string | Symbol> = new Set(<const>[
+  "connect",
+  "connect_error",
+  "disconnect",
+  "disconnecting",
+  "newListener",
+  "removeListener",
+]);
+
+export class BroadcastOperator<
+  EmitEvents extends EventsMap,
+  ServerSideEvents extends EventsMap,
+> implements TypedEventBroadcaster<EmitEvents>
+{
+  constructor(
+    private readonly publish: (
+      message: DistributiveOmit<ClusterMessage, "uid" | "nsp">,
+    ) => void,
+    private readonly rooms: Set<string> = new Set<string>(),
+    private readonly exceptRooms: Set<string> = new Set<string>(),
+    private readonly flags: BroadcastFlags = {},
+  ) {}
+
+  /**
+   * Targets a room when emitting.
+   *
+   * @param room
+   * @return a new BroadcastOperator instance
+   * @public
+   */
+  public to(
+    room: string | string[],
+  ): BroadcastOperator<EmitEvents, ServerSideEvents> {
+    const rooms = new Set(this.rooms);
+    if (Array.isArray(room)) {
+      room.forEach((r) => rooms.add(r));
+    } else {
+      rooms.add(room);
+    }
+    return new BroadcastOperator(
+      this.publish,
+      rooms,
+      this.exceptRooms,
+      this.flags,
+    );
+  }
+
+  /**
+   * Targets a room when emitting.
+   *
+   * @param room
+   * @return a new BroadcastOperator instance
+   * @public
+   */
+  public in(
+    room: string | string[],
+  ): BroadcastOperator<EmitEvents, ServerSideEvents> {
+    return this.to(room);
+  }
+
+  /**
+   * Excludes a room when emitting.
+   *
+   * @param room
+   * @return a new BroadcastOperator instance
+   * @public
+   */
+  public except(
+    room: string | string[],
+  ): BroadcastOperator<EmitEvents, ServerSideEvents> {
+    const exceptRooms = new Set(this.exceptRooms);
+    if (Array.isArray(room)) {
+      room.forEach((r) => exceptRooms.add(r));
+    } else {
+      exceptRooms.add(room);
+    }
+    return new BroadcastOperator(
+      this.publish,
+      this.rooms,
+      exceptRooms,
+      this.flags,
+    );
+  }
+
+  /**
+   * Sets the compress flag.
+   *
+   * @param compress - if `true`, compresses the sending data
+   * @return a new BroadcastOperator instance
+   * @public
+   */
+  public compress(
+    compress: boolean,
+  ): BroadcastOperator<EmitEvents, ServerSideEvents> {
+    const flags = Object.assign({}, this.flags, { compress });
+    return new BroadcastOperator(
+      this.publish,
+      this.rooms,
+      this.exceptRooms,
+      flags,
+    );
+  }
+
+  /**
+   * Sets a modifier for a subsequent event emission that the event data may be lost if the client is not ready to
+   * receive messages (because of network slowness or other issues, or because they’re connected through long polling
+   * and is in the middle of a request-response cycle).
+   *
+   * @return a new BroadcastOperator instance
+   * @public
+   */
+  public get volatile(): BroadcastOperator<EmitEvents, ServerSideEvents> {
+    const flags = Object.assign({}, this.flags, { volatile: true });
+    return new BroadcastOperator(
+      this.publish,
+      this.rooms,
+      this.exceptRooms,
+      flags,
+    );
+  }
+
+  /**
+   * Emits to all clients.
+   *
+   * @return Always true
+   * @public
+   */
+  public emit<Ev extends EventNames<EmitEvents>>(
+    ev: Ev,
+    ...args: EventParams<EmitEvents, Ev>
+  ): true {
+    if (RESERVED_EVENTS.has(ev)) {
+      throw new Error(`"${String(ev)}" is a reserved event name`);
+    }
+
+    // set up packet object
+    const data = [ev, ...args];
+    const packet = {
+      type: 2, // EVENT
+      data: data,
+    };
+
+    const opts = {
+      rooms: [...this.rooms],
+      flags: this.flags,
+      except: [...this.exceptRooms],
+    };
+
+    this.publish({
+      type: MessageType.BROADCAST,
+      data: {
+        packet,
+        opts,
+      },
+    });
+
+    return true;
+  }
+
+  /**
+   * Makes the matching socket instances join the specified rooms
+   *
+   * @param rooms
+   * @public
+   */
+  public socketsJoin(rooms: string | string[]): void {
+    this.publish({
+      type: MessageType.SOCKETS_JOIN,
+      data: {
+        opts: {
+          rooms: [...this.rooms],
+          except: [...this.exceptRooms],
+          flags: {},
+        },
+        rooms: Array.isArray(rooms) ? rooms : [rooms],
+      },
+    });
+  }
+
+  /**
+   * Makes the matching socket instances leave the specified rooms
+   *
+   * @param rooms
+   * @public
+   */
+  public socketsLeave(rooms: string | string[]): void {
+    this.publish({
+      type: MessageType.SOCKETS_LEAVE,
+      data: {
+        opts: {
+          rooms: [...this.rooms],
+          except: [...this.exceptRooms],
+          flags: {},
+        },
+        rooms: Array.isArray(rooms) ? rooms : [rooms],
+      },
+    });
+  }
+
+  /**
+   * Makes the matching socket instances disconnect
+   *
+   * @param close - whether to close the underlying connection
+   * @public
+   */
+  public disconnectSockets(close: boolean = false): void {
+    this.publish({
+      type: MessageType.DISCONNECT_SOCKETS,
+      data: {
+        opts: {
+          rooms: [...this.rooms],
+          except: [...this.exceptRooms],
+          flags: {},
+        },
+        close,
+      },
+    });
+  }
+
+  /**
+   * Send a packet to the Socket.IO servers in the cluster
+   *
+   * @param ev - the event name
+   * @param args - any number of serializable arguments
+   */
+  public serverSideEmit<Ev extends EventNames<ServerSideEvents>>(
+    ev: Ev,
+    ...args: EventParams<ServerSideEvents, Ev>
+  ): void {
+    const withAck = args.length && typeof args[args.length - 1] === "function";
+
+    if (withAck) {
+      throw new Error("Acknowledgements are not supported");
+    }
+
+    this.publish({
+      type: MessageType.SERVER_SIDE_EMIT,
+      data: {
+        packet: [ev, ...args],
+      },
+    });
+  }
+}
+
+function flattenPayload(message: ClusterMessage) {
+  const rawMessage = {
+    uid: message.uid,
+    nsp: message.nsp,
+    type: message.type.toString(),
+    data: undefined as string | undefined,
+  };
+
+  // @ts-expect-error
+  const data = message.data;
+
+  if (data) {
+    const mayContainBinary = [
+      MessageType.BROADCAST,
+      MessageType.FETCH_SOCKETS_RESPONSE,
+      MessageType.SERVER_SIDE_EMIT,
+      MessageType.SERVER_SIDE_EMIT_RESPONSE,
+      MessageType.BROADCAST_ACK,
+    ].includes(message.type);
+
+    if (mayContainBinary && hasBinary(data)) {
+      rawMessage.data = Buffer.from(encode(data)).toString("base64");
+    } else {
+      rawMessage.data = JSON.stringify(data);
+    }
+  }
+
+  return rawMessage;
+}
+
+export interface RedisStreamsEmitterOptions {
+  /**
+   * The name of the Redis stream.
+   * @default "socket.io"
+   */
+  streamName?: string;
+  /**
+   * The maximum size of the stream. Almost exact trimming (~) is used.
+   * @default 10_000
+   */
+  maxLen?: number;
+}
+
+export class Emitter<
+  EmitEvents extends EventsMap = DefaultEventsMap,
+  ServerSideEvents extends EventsMap = DefaultEventsMap,
+> extends BaseEmitter<EmitEvents, ServerSideEvents> {
+  readonly #redisClient: any;
+  readonly #opts: Required<RedisStreamsEmitterOptions>;
+  readonly #nsp: string;
+
+  constructor(
+    redisClient: any,
+    opts: RedisStreamsEmitterOptions = {},
+    nsp = "/",
+  ) {
+    super();
+    this.#redisClient = redisClient;
+    this.#opts = Object.assign(
+      {
+        streamName: "socket.io",
+        maxLen: 10_000,
+      },
+      opts,
+    );
+    this.#nsp = nsp;
+  }
+
+  public of(nsp: string) {
+    return new Emitter(this.#redisClient, this.#opts, nsp);
+  }
+
+  protected override publish(
+    message: DistributiveOmit<ClusterMessage, "uid" | "nsp">,
+  ) {
+    (message as ClusterMessage).uid = EMITTER_UID;
+    (message as ClusterMessage).nsp = this.#nsp;
+
+    debug(
+      "publishing message %s to stream %s",
+      message.type,
+      this.#opts.streamName,
+    );
+
+    if (message.type === MessageType.BROADCAST) {
+      // @ts-expect-error FIXME untyped packet object
+      message.data.packet.nsp = this.#nsp;
+    }
+
+    return XADD(
+      this.#redisClient,
+      this.#opts.streamName,
+      flattenPayload(message as ClusterMessage),
+      this.#opts.maxLen,
+    );
+  }
+}

packages/socket.io-redis-streams-emitter/lib/typed-events.ts

@@ -0,0 +1,37 @@
+/**
+ * An events map is an interface that maps event names to their value, which
+ * represents the type of the `on` listener.
+ */
+export interface EventsMap {
+  [event: string]: any;
+}
+
+/**
+ * The default events map, used if no EventsMap is given. Using this EventsMap
+ * is equivalent to accepting all event names, and any data.
+ */
+export interface DefaultEventsMap {
+  [event: string]: (...args: any[]) => void;
+}
+
+/**
+ * Returns a union type containing all the keys of an event map.
+ */
+export type EventNames<Map extends EventsMap> = keyof Map & (string | symbol);
+
+/** The tuple type representing the parameters of an event listener */
+export type EventParams<
+  Map extends EventsMap,
+  Ev extends EventNames<Map>,
+> = Parameters<Map[Ev]>;
+
+/**
+ * Interface for classes that aren't `EventEmitter`s, but still expose a
+ * strictly typed `emit` method.
+ */
+export interface TypedEventBroadcaster<EmitEvents extends EventsMap> {
+  emit<Ev extends EventNames<EmitEvents>>(
+    ev: Ev,
+    ...args: EventParams<EmitEvents, Ev>
+  ): boolean;
+}

packages/socket.io-redis-streams-emitter/lib/util.ts

@@ -0,0 +1,68 @@
+export function hasBinary(obj: any, toJSON?: boolean): boolean {
+  if (!obj || typeof obj !== "object") {
+    return false;
+  }
+
+  if (obj instanceof ArrayBuffer || ArrayBuffer.isView(obj)) {
+    return true;
+  }
+
+  if (Array.isArray(obj)) {
+    for (let i = 0, l = obj.length; i < l; i++) {
+      if (hasBinary(obj[i])) {
+        return true;
+      }
+    }
+    return false;
+  }
+
+  for (const key in obj) {
+    if (Object.prototype.hasOwnProperty.call(obj, key) && hasBinary(obj[key])) {
+      return true;
+    }
+  }
+
+  if (obj.toJSON && typeof obj.toJSON === "function" && !toJSON) {
+    return hasBinary(obj.toJSON(), true);
+  }
+
+  return false;
+}
+
+/**
+ * Whether the client comes from the `redis` package
+ *
+ * @param redisClient
+ *
+ * @see https://github.com/redis/node-redis
+ */
+function isRedisV4Client(redisClient: any) {
+  return typeof redisClient.sSubscribe === "function";
+}
+
+/**
+ * @see https://redis.io/commands/xadd/
+ */
+export function XADD(
+  redisClient: any,
+  streamName: string,
+  payload: any,
+  maxLenThreshold: number,
+) {
+  if (isRedisV4Client(redisClient)) {
+    return redisClient.xAdd(streamName, "*", payload, {
+      TRIM: {
+        strategy: "MAXLEN",
+        strategyModifier: "~",
+        threshold: maxLenThreshold,
+      },
+    });
+  } else {
+    const args = [streamName, "MAXLEN", "~", maxLenThreshold, "*"];
+    Object.keys(payload).forEach((k) => {
+      args.push(k, payload[k]);
+    });
+
+    return redisClient.xadd.call(redisClient, args);
+  }
+}

packages/socket.io-redis-streams-emitter/package.json

@@ -0,0 +1,38 @@
+{
+  "name": "@socket.io/redis-streams-emitter",
+  "version": "0.1.0",
+  "description": "The Socket.IO Redis streams emitter, allowing to communicate with a group of Socket.IO servers from another Node.js process",
+  "license": "MIT",
+  "homepage": "https://github.com/socketio/socket.io/tree/main/packages/socket.io-redis-streams-emitter#readme",
+  "repository": {
+    "type": "git",
+    "url": "git+https://github.com/socketio/socket.io.git"
+  },
+  "files": [
+    "dist/"
+  ],
+  "main": "./dist/index.js",
+  "types": "./dist/index.d.ts",
+  "scripts": {
+    "compile": "rimraf ./dist && tsc",
+    "format:check": "prettier --parser typescript --check 'lib/**/*.ts' 'test/**/*.ts'",
+    "format:fix": "prettier --parser typescript --write 'lib/**/*.ts' 'test/**/*.ts'",
+    "prepack": "npm run compile",
+    "test": "npm run format:check && npm run compile && npm run test:redis-standalone && npm run test:ioredis-standalone",
+    "test:redis-standalone": "nyc mocha --import=tsx test/**/*.ts",
+    "test:redis-cluster": "REDIS_CLUSTER=1 mocha --import=tsx test/**/*.ts",
+    "test:ioredis-standalone": "REDIS_LIB=ioredis mocha --import=tsx test/**/*.ts",
+    "test:ioredis-cluster": "REDIS_LIB=ioredis REDIS_CLUSTER=1 mocha --import=tsx test/**/*.ts",
+    "test:valkey-standalone": "VALKEY=1 mocha --import=tsx test/**/*.ts"
+  },
+  "dependencies": {
+    "@msgpack/msgpack": "~2.8.0",
+    "debug": "~4.4.1"
+  },
+  "keywords": [
+    "socket.io",
+    "redis",
+    "redis-streams",
+    "emitter"
+  ]
+}

packages/socket.io-redis-streams-emitter/test/index.ts

@@ -0,0 +1,225 @@
+import { type Server, type Socket as ServerSocket } from "socket.io";
+import { type Socket as ClientSocket } from "socket.io-client";
+import expect = require("expect.js");
+import { times, sleep, setup, initRedisClient } from "./util";
+import { Emitter } from "../lib";
+
+const PROPAGATION_DELAY_IN_MS = 100;
+
+describe("@socket.io/redis-streams-emitter", () => {
+  let servers: Server[],
+    serverSockets: ServerSocket[],
+    clientSockets: ClientSocket[],
+    cleanup: () => void,
+    emitter: Emitter;
+
+  beforeEach(async () => {
+    const testContext = await setup();
+    servers = testContext.servers;
+    serverSockets = testContext.serverSockets;
+    clientSockets = testContext.clientSockets;
+    const redisClient = await initRedisClient();
+    emitter = new Emitter(redisClient);
+
+    cleanup = () => {
+      testContext.cleanup();
+      redisClient.quit();
+    };
+  });
+
+  afterEach(() => cleanup());
+
+  describe("broadcast", function () {
+    it("broadcasts to all clients", (done) => {
+      const partialDone = times(3, done);
+
+      clientSockets.forEach((clientSocket) => {
+        clientSocket.on("test", (arg1, arg2, arg3) => {
+          expect(arg1).to.eql(1);
+          expect(arg2).to.eql("2");
+          expect(Buffer.isBuffer(arg3)).to.be(true);
+          partialDone();
+        });
+      });
+
+      emitter.emit("test", 1, "2", Buffer.from([3, 4]));
+    });
+
+    it("broadcasts to all clients in a namespace", (done) => {
+      const partialDone = times(3, () => {
+        servers.forEach((server) => server.of("/custom").adapter.close());
+        done();
+      });
+
+      servers.forEach((server) => server.of("/custom"));
+
+      const onConnect = times(3, async () => {
+        await sleep(PROPAGATION_DELAY_IN_MS);
+
+        emitter.of("/custom").emit("test");
+      });
+
+      clientSockets.forEach((clientSocket) => {
+        const socket = clientSocket.io.socket("/custom");
+        socket.on("connect", onConnect);
+        socket.on("test", () => {
+          socket.disconnect();
+          partialDone();
+        });
+      });
+    });
+
+    it("broadcasts to all clients in a room", (done) => {
+      serverSockets[1].join("room1");
+
+      clientSockets[0].on("test", () => {
+        done(new Error("should not happen"));
+      });
+
+      clientSockets[1].on("test", () => {
+        done();
+      });
+
+      clientSockets[2].on("test", () => {
+        done(new Error("should not happen"));
+      });
+
+      emitter.to("room1").emit("test");
+    });
+
+    it("broadcasts to all clients except in room", (done) => {
+      const partialDone = times(2, done);
+      serverSockets[1].join("room1");
+
+      clientSockets[0].on("test", () => {
+        partialDone();
+      });
+
+      clientSockets[1].on("test", () => {
+        done(new Error("should not happen"));
+      });
+
+      clientSockets[2].on("test", () => {
+        partialDone();
+      });
+
+      emitter.of("/").except("room1").emit("test");
+    });
+  });
+
+  describe("socketsJoin", () => {
+    it("makes all socket instances join the specified room", async () => {
+      emitter.socketsJoin("room1");
+
+      await sleep(PROPAGATION_DELAY_IN_MS);
+
+      expect(serverSockets[0].rooms.has("room1")).to.be(true);
+      expect(serverSockets[1].rooms.has("room1")).to.be(true);
+      expect(serverSockets[2].rooms.has("room1")).to.be(true);
+    });
+
+    it("makes the matching socket instances join the specified room", async () => {
+      serverSockets[0].join("room1");
+      serverSockets[2].join("room1");
+
+      emitter.in("room1").socketsJoin("room2");
+
+      await sleep(PROPAGATION_DELAY_IN_MS);
+
+      expect(serverSockets[0].rooms.has("room2")).to.be(true);
+      expect(serverSockets[1].rooms.has("room2")).to.be(false);
+      expect(serverSockets[2].rooms.has("room2")).to.be(true);
+    });
+
+    it("makes the given socket instance join the specified room", async () => {
+      emitter.in(serverSockets[1].id).socketsJoin("room3");
+
+      await sleep(PROPAGATION_DELAY_IN_MS);
+
+      expect(serverSockets[0].rooms.has("room3")).to.be(false);
+      expect(serverSockets[1].rooms.has("room3")).to.be(true);
+      expect(serverSockets[2].rooms.has("room3")).to.be(false);
+    });
+  });
+
+  describe("socketsLeave", () => {
+    it("makes all socket instances leave the specified room", async () => {
+      serverSockets[0].join("room1");
+      serverSockets[2].join("room1");
+
+      emitter.socketsLeave("room1");
+
+      await sleep(PROPAGATION_DELAY_IN_MS);
+
+      expect(serverSockets[0].rooms.has("room1")).to.be(false);
+      expect(serverSockets[1].rooms.has("room1")).to.be(false);
+      expect(serverSockets[2].rooms.has("room1")).to.be(false);
+    });
+
+    it("makes the matching socket instances leave the specified room", async () => {
+      serverSockets[0].join(["room1", "room2"]);
+      serverSockets[1].join(["room1", "room2"]);
+      serverSockets[2].join(["room2"]);
+
+      emitter.in("room1").socketsLeave("room2");
+
+      await sleep(PROPAGATION_DELAY_IN_MS);
+
+      expect(serverSockets[0].rooms.has("room2")).to.be(false);
+      expect(serverSockets[1].rooms.has("room2")).to.be(false);
+      expect(serverSockets[2].rooms.has("room2")).to.be(true);
+    });
+
+    it("makes the given socket instance leave the specified room", async () => {
+      serverSockets[0].join("room3");
+      serverSockets[1].join("room3");
+      serverSockets[2].join("room3");
+
+      emitter.in(serverSockets[1].id).socketsLeave("room3");
+
+      await sleep(PROPAGATION_DELAY_IN_MS);
+
+      expect(serverSockets[0].rooms.has("room3")).to.be(true);
+      expect(serverSockets[1].rooms.has("room3")).to.be(false);
+      expect(serverSockets[2].rooms.has("room3")).to.be(true);
+    });
+  });
+
+  describe("disconnectSockets", () => {
+    it("makes all socket instances disconnect", (done) => {
+      const partialDone = times(3, done);
+
+      clientSockets.forEach((clientSocket) => {
+        clientSocket.on("disconnect", (reason) => {
+          expect(reason).to.eql("io server disconnect");
+          partialDone();
+        });
+      });
+
+      emitter.disconnectSockets();
+    });
+  });
+
+  describe("serverSideEmit", () => {
+    it("sends an event to other server instances", (done) => {
+      const partialDone = times(3, done);
+
+      emitter.serverSideEmit("hello", "world", 1, "2");
+
+      servers[0].on("hello", (arg1, arg2, arg3) => {
+        expect(arg1).to.eql("world");
+        expect(arg2).to.eql(1);
+        expect(arg3).to.eql("2");
+        partialDone();
+      });
+
+      servers[1].on("hello", (arg1, arg2, arg3) => {
+        partialDone();
+      });
+
+      servers[2].of("/").on("hello", () => {
+        partialDone();
+      });
+    });
+  });
+});

packages/socket.io-redis-streams-emitter/test/util.ts

@@ -0,0 +1,156 @@
+import { createServer } from "node:http";
+import { type AddressInfo } from "node:net";
+import { createClient, createCluster } from "redis";
+import { Redis, Cluster } from "ioredis";
+import { Server, type Socket as ServerSocket } from "socket.io";
+import { io as ioc, type Socket as ClientSocket } from "socket.io-client";
+import { createAdapter } from "@socket.io/redis-streams-adapter";
+
+export function times(count: number, fn: () => void) {
+  let i = 0;
+  return () => {
+    i++;
+    if (i === count) {
+      fn();
+    } else if (i > count) {
+      throw new Error(`too many calls: ${i} instead of ${count}`);
+    }
+  };
+}
+
+export function sleep(duration: number) {
+  return new Promise((resolve) => setTimeout(resolve, duration));
+}
+
+const mode = process.env.REDIS_CLUSTER === "1" ? "cluster" : "standalone";
+const lib = process.env.REDIS_LIB || "redis";
+
+console.log(`[INFO] testing in ${mode} mode with ${lib}`);
+
+export async function initRedisClient() {
+  if (mode === "cluster") {
+    if (lib === "ioredis") {
+      return new Cluster([
+        {
+          host: "localhost",
+          port: 7000,
+        },
+        {
+          host: "localhost",
+          port: 7001,
+        },
+        {
+          host: "localhost",
+          port: 7002,
+        },
+        {
+          host: "localhost",
+          port: 7003,
+        },
+        {
+          host: "localhost",
+          port: 7004,
+        },
+        {
+          host: "localhost",
+          port: 7005,
+        },
+      ]);
+    } else {
+      const redisClient = createCluster({
+        rootNodes: [
+          {
+            url: "redis://localhost:7000",
+          },
+          {
+            url: "redis://localhost:7001",
+          },
+          {
+            url: "redis://localhost:7002",
+          },
+          {
+            url: "redis://localhost:7003",
+          },
+          {
+            url: "redis://localhost:7004",
+          },
+          {
+            url: "redis://localhost:7005",
+          },
+        ],
+      });
+
+      await redisClient.connect();
+
+      return redisClient;
+    }
+  } else {
+    if (lib === "ioredis") {
+      return new Redis();
+    } else {
+      const port = process.env.VALKEY === "1" ? 6389 : 6379;
+      const redisClient = createClient({
+        url: `redis://localhost:${port}`,
+      });
+      await redisClient.connect();
+
+      return redisClient;
+    }
+  }
+}
+
+async function init() {
+  const redisClient = await initRedisClient();
+
+  const httpServer = createServer();
+  const io = new Server(httpServer, {
+    adapter: createAdapter(redisClient, {
+      readCount: 1, // return as soon as possible
+    }),
+  });
+
+  return new Promise<{
+    io: Server;
+    socket: ServerSocket;
+    clientSocket: ClientSocket;
+    cleanup: () => void;
+  }>((resolve) => {
+    httpServer.listen(() => {
+      const port = (httpServer.address() as AddressInfo).port;
+      const clientSocket = ioc(`http://localhost:${port}`);
+
+      io.on("connection", async (socket) => {
+        resolve({
+          io,
+          socket,
+          clientSocket,
+          cleanup: () => {
+            io.close();
+            clientSocket.disconnect();
+            redisClient.quit();
+          },
+        });
+      });
+    });
+  });
+}
+
+export async function setup() {
+  const results = await Promise.all([init(), init(), init()]);
+
+  const servers = results.map(({ io }) => io);
+  const serverSockets = results.map(({ socket }) => socket);
+  const clientSockets = results.map(({ clientSocket }) => clientSocket);
+  const cleanupMethods = results.map(({ cleanup }) => cleanup);
+
+  return {
+    servers,
+    serverSockets,
+    clientSockets,
+    cleanup: () => {
+      for (const cleanup of cleanupMethods) {
+        cleanup();
+      }
+    },
+  };
+}

packages/socket.io-redis-streams-emitter/tsconfig.json

@@ -0,0 +1,13 @@
+{
+  "compilerOptions": {
+    "outDir": "./dist",
+    "allowJs": false,
+    "target": "es2017",
+    "module": "commonjs",
+    "declaration": true,
+    "strict": true
+  },
+  "include": [
+    "./lib/**/*"
+  ]
+}

packages/socket.io/lib/namespace.ts

@@ -197,6 +197,10 @@ export class Namespace<
   _initAdapter(): void {
     // @ts-ignore
     this.adapter = new (this.server.adapter()!)(this);
+
+    Promise.resolve(this.adapter.init()).catch((err) => {
+      debug("error while initializing adapter: %s", err);
+    });
   }
 
   /**

packages/socket.io/package.json

@@ -53,7 +53,7 @@
     "accepts": "~1.3.4",
     "base64id": "~2.0.0",
     "cors": "~2.8.5",
-    "debug": "~4.3.2",
+    "debug": "~4.4.1",
     "engine.io": "~6.6.0",
     "socket.io-adapter": "~2.5.2",
     "socket.io-parser": "~4.2.4"