chore(release): @socket.io/cluster-adapter@0.3.0

Diff: https://github.com/socketio/socket.io-cluster-adapter/compare/0.2.2...0.3.0
Merge remote-tracking branch 'socket.io-cluster-adapter/monorepo'
2026-01-12 00:17:56 -05:00 · 2025-10-16 19:55:56 +02:00 · 2025-10-16 19:35:51 +02:00 · 2025-10-16 19:31:30 +02:00 · 2025-10-16 19:16:20 +02:00 · 2025-10-16 12:03:32 +02:00
62 changed files with 10665 additions and 2271 deletions
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -22,7 +22,7 @@ jobs:
        node-version:
          - 18
          - 20
-          - 22
+          - 22.17.1 # experimental TS type striping in 22.18.0 breaks the build

    services:
      redis:
@@ -35,6 +35,18 @@ jobs:
        ports:
          - 6379:6379

+      postgres:
+        image: postgres:14
+        env:
+          POSTGRES_PASSWORD: changeit
+        options: >-
+          --health-cmd pg_isready
+          --health-interval 10s
+          --health-timeout 5s
+          --health-retries 5
+        ports:
+          - 5432:5432
+
    steps:
      - name: Checkout repository
        uses: actions/checkout@v4
--- a/CHANGELOG.md
+++ b/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)          |
--- a/docs/engine.io-protocol/v4-test-suite/test-suite.js
+++ b/docs/engine.io-protocol/v4-test-suite/test-suite.js
@@ -17,16 +17,35 @@ function sleep(delay) {
  return new Promise((resolve) => setTimeout(resolve, delay));
 }

+function createWebSocket(url) {
+  const socket = new WebSocket(url);
+  socket._eventBuffer = {};
+  socket._pendingPromises = {};
+
+  for (const eventType of ["open", "close", "message"]) {
+    socket._eventBuffer[eventType] = [];
+    socket._pendingPromises[eventType] = [];
+
+    socket.addEventListener(eventType, (event) => {
+      if (socket._pendingPromises[eventType].length) {
+        socket._pendingPromises[eventType].shift()(event);
+      } else {
+        socket._eventBuffer[eventType].push(event);
+      }
+    });
+  }
+
+  return socket;
+}
+
 function waitFor(socket, eventType) {
-  return new Promise((resolve) => {
-    socket.addEventListener(
-      eventType,
-      (event) => {
-        resolve(event);
-      },
-      { once: true }
-    );
-  });
+  if (socket._eventBuffer[eventType].length) {
+    return Promise.resolve(socket._eventBuffer[eventType].shift());
+  } else {
+    return new Promise((resolve) => {
+      socket._pendingPromises[eventType].push(resolve);
+    });
+  }
 }

 async function initLongPollingSession() {
@@ -110,7 +129,7 @@ describe("Engine.IO protocol", () => {

    describe("WebSocket", () => {
      it("successfully opens a session", async () => {
-        const socket = new WebSocket(
+        const socket = createWebSocket(
          `${WS_URL}/engine.io/?EIO=4&transport=websocket`
        );

@@ -137,7 +156,7 @@ describe("Engine.IO protocol", () => {
      });

      it("fails with an invalid 'EIO' query parameter", async () => {
-        const socket = new WebSocket(
+        const socket = createWebSocket(
          `${WS_URL}/engine.io/?transport=websocket`
        );

@@ -145,9 +164,9 @@ describe("Engine.IO protocol", () => {
          socket.on("error", () => {});
        }

-        waitFor(socket, "close");
+        await waitFor(socket, "close");

-        const socket2 = new WebSocket(
+        const socket2 = createWebSocket(
          `${WS_URL}/engine.io/?EIO=abc&transport=websocket`
        );

@@ -155,19 +174,19 @@ describe("Engine.IO protocol", () => {
          socket2.on("error", () => {});
        }

-        waitFor(socket2, "close");
+        await waitFor(socket2, "close");
      });

      it("fails with an invalid 'transport' query parameter", async () => {
-        const socket = new WebSocket(`${WS_URL}/engine.io/?EIO=4`);
+        const socket = createWebSocket(`${WS_URL}/engine.io/?EIO=4`);

        if (isNodejs) {
          socket.on("error", () => {});
        }

-        waitFor(socket, "close");
+        await waitFor(socket, "close");

-        const socket2 = new WebSocket(
+        const socket2 = createWebSocket(
          `${WS_URL}/engine.io/?EIO=4&transport=abc`
        );

@@ -175,7 +194,7 @@ describe("Engine.IO protocol", () => {
          socket2.on("error", () => {});
        }

-        waitFor(socket2, "close");
+        await waitFor(socket2, "close");
      });
    });
  });
@@ -313,11 +332,30 @@ describe("Engine.IO protocol", () => {

        expect(pollResponse.status).to.eql(400);
      });
+
+      it("closes the session upon cancelled polling request", async () => {
+        const sid = await initLongPollingSession();
+        const controller = new AbortController();
+
+        fetch(`${URL}/engine.io/?EIO=4&transport=polling&sid=${sid}`, {
+          signal: controller.signal,
+        }).catch(() => {});
+
+        await sleep(5);
+
+        controller.abort();
+
+        const pollResponse = await fetch(
+          `${URL}/engine.io/?EIO=4&transport=polling&sid=${sid}`,
+        );
+
+        expect(pollResponse.status).to.eql(400);
+      });
    });

    describe("WebSocket", () => {
      it("sends and receives a plain text packet", async () => {
-        const socket = new WebSocket(
+        const socket = createWebSocket(
          `${WS_URL}/engine.io/?EIO=4&transport=websocket`
        );

@@ -335,7 +373,7 @@ describe("Engine.IO protocol", () => {
      });

      it("sends and receives a binary packet", async () => {
-        const socket = new WebSocket(
+        const socket = createWebSocket(
          `${WS_URL}/engine.io/?EIO=4&transport=websocket`
        );
        socket.binaryType = "arraybuffer";
@@ -352,7 +390,7 @@ describe("Engine.IO protocol", () => {
      });

      it("closes the session upon invalid packet format", async () => {
-        const socket = new WebSocket(
+        const socket = createWebSocket(
          `${WS_URL}/engine.io/?EIO=4&transport=websocket`
        );

@@ -412,7 +450,7 @@ describe("Engine.IO protocol", () => {

    describe("WebSocket", () => {
      it("sends ping/pong packets", async () => {
-        const socket = new WebSocket(
+        const socket = createWebSocket(
          `${WS_URL}/engine.io/?EIO=4&transport=websocket`
        );

@@ -430,7 +468,7 @@ describe("Engine.IO protocol", () => {
      });

      it("closes the session upon ping timeout", async () => {
-        const socket = new WebSocket(
+        const socket = createWebSocket(
          `${WS_URL}/engine.io/?EIO=4&transport=websocket`
        );

@@ -468,7 +506,7 @@ describe("Engine.IO protocol", () => {

    describe("WebSocket", () => {
      it("forcefully closes the session", async () => {
-        const socket = new WebSocket(
+        const socket = createWebSocket(
          `${WS_URL}/engine.io/?EIO=4&transport=websocket`
        );

@@ -485,7 +523,7 @@ describe("Engine.IO protocol", () => {
    it("successfully upgrades from HTTP long-polling to WebSocket", async () => {
      const sid = await initLongPollingSession();

-      const socket = new WebSocket(
+      const socket = createWebSocket(
        `${WS_URL}/engine.io/?EIO=4&transport=websocket&sid=${sid}`
      );

@@ -521,12 +559,13 @@ describe("Engine.IO protocol", () => {
    it("ignores HTTP requests with same sid after upgrade", async () => {
      const sid = await initLongPollingSession();

-      const socket = new WebSocket(
+      const socket = createWebSocket(
        `${WS_URL}/engine.io/?EIO=4&transport=websocket&sid=${sid}`
      );

      await waitFor(socket, "open");
      socket.send("2probe");
+      await waitFor(socket, "message"); // "3probe"
      socket.send("5");

      const pollResponse = await fetch(
@@ -545,15 +584,16 @@ describe("Engine.IO protocol", () => {
    it("ignores WebSocket connection with same sid after upgrade", async () => {
      const sid = await initLongPollingSession();

-      const socket = new WebSocket(
+      const socket = createWebSocket(
        `${WS_URL}/engine.io/?EIO=4&transport=websocket&sid=${sid}`
      );

      await waitFor(socket, "open");
      socket.send("2probe");
+      await waitFor(socket, "message"); // "3probe"
      socket.send("5");

-      const socket2 = new WebSocket(
+      const socket2 = createWebSocket(
        `${WS_URL}/engine.io/?EIO=4&transport=websocket&sid=${sid}`
      );

--- a/docs/socket.io-protocol/v5-test-suite/test-suite.js
+++ b/docs/socket.io-protocol/v5-test-suite/test-suite.js
@@ -17,16 +17,35 @@ function sleep(delay) {
  return new Promise((resolve) => setTimeout(resolve, delay));
 }

+function createWebSocket(url) {
+  const socket = new WebSocket(url);
+  socket._eventBuffer = {};
+  socket._pendingPromises = {};
+
+  for (const eventType of ["open", "close", "message"]) {
+    socket._eventBuffer[eventType] = [];
+    socket._pendingPromises[eventType] = [];
+
+    socket.addEventListener(eventType, (event) => {
+      if (socket._pendingPromises[eventType].length) {
+        socket._pendingPromises[eventType].shift()(event);
+      } else {
+        socket._eventBuffer[eventType].push(event);
+      }
+    });
+  }
+
+  return socket;
+}
+
 function waitFor(socket, eventType) {
-  return new Promise((resolve) => {
-    socket.addEventListener(
-      eventType,
-      (event) => {
-        resolve(event);
-      },
-      { once: true }
-    );
-  });
+  if (socket._eventBuffer[eventType].length) {
+    return Promise.resolve(socket._eventBuffer[eventType].shift());
+  } else {
+    return new Promise((resolve) => {
+      socket._pendingPromises[eventType].push(resolve);
+    });
+  }
 }

 function waitForPackets(socket, count) {
@@ -55,7 +74,7 @@ async function initLongPollingSession() {
 }

 async function initSocketIOConnection() {
-  const socket = new WebSocket(
+  const socket = createWebSocket(
    `${WS_URL}/socket.io/?EIO=4&transport=websocket`
  );
  socket.binaryType = "arraybuffer";
@@ -145,7 +164,7 @@ describe("Engine.IO protocol", () => {

    describe("WebSocket", () => {
      it("should successfully open a session", async () => {
-        const socket = new WebSocket(
+        const socket = createWebSocket(
          `${WS_URL}/socket.io/?EIO=4&transport=websocket`
        );

@@ -172,7 +191,7 @@ describe("Engine.IO protocol", () => {
      });

      it("should fail with an invalid 'EIO' query parameter", async () => {
-        const socket = new WebSocket(
+        const socket = createWebSocket(
          `${WS_URL}/socket.io/?transport=websocket`
        );

@@ -180,9 +199,9 @@ describe("Engine.IO protocol", () => {
          socket.on("error", () => {});
        }

-        waitFor(socket, "close");
+        await waitFor(socket, "close");

-        const socket2 = new WebSocket(
+        const socket2 = createWebSocket(
          `${WS_URL}/socket.io/?EIO=abc&transport=websocket`
        );

@@ -190,19 +209,19 @@ describe("Engine.IO protocol", () => {
          socket2.on("error", () => {});
        }

-        waitFor(socket2, "close");
+        await waitFor(socket2, "close");
      });

      it("should fail with an invalid 'transport' query parameter", async () => {
-        const socket = new WebSocket(`${WS_URL}/socket.io/?EIO=4`);
+        const socket = createWebSocket(`${WS_URL}/socket.io/?EIO=4`);

        if (isNodejs) {
          socket.on("error", () => {});
        }

-        waitFor(socket, "close");
+        await waitFor(socket, "close");

-        const socket2 = new WebSocket(
+        const socket2 = createWebSocket(
          `${WS_URL}/socket.io/?EIO=4&transport=abc`
        );

@@ -210,7 +229,7 @@ describe("Engine.IO protocol", () => {
          socket2.on("error", () => {});
        }

-        waitFor(socket2, "close");
+        await waitFor(socket2, "close");
      });
    });
  });
@@ -260,7 +279,7 @@ describe("Engine.IO protocol", () => {

    describe("WebSocket", () => {
      it("should send ping/pong packets", async () => {
-        const socket = new WebSocket(
+        const socket = createWebSocket(
          `${WS_URL}/socket.io/?EIO=4&transport=websocket`
        );

@@ -278,7 +297,7 @@ describe("Engine.IO protocol", () => {
      });

      it("should close the session upon ping timeout", async () => {
-        const socket = new WebSocket(
+        const socket = createWebSocket(
          `${WS_URL}/socket.io/?EIO=4&transport=websocket`
        );

@@ -316,7 +335,7 @@ describe("Engine.IO protocol", () => {

    describe("WebSocket", () => {
      it("should forcefully close the session", async () => {
-        const socket = new WebSocket(
+        const socket = createWebSocket(
          `${WS_URL}/socket.io/?EIO=4&transport=websocket`
        );

@@ -333,7 +352,7 @@ describe("Engine.IO protocol", () => {
    it("should successfully upgrade from HTTP long-polling to WebSocket", async () => {
      const sid = await initLongPollingSession();

-      const socket = new WebSocket(
+      const socket = createWebSocket(
        `${WS_URL}/socket.io/?EIO=4&transport=websocket&sid=${sid}`
      );

@@ -353,12 +372,13 @@ describe("Engine.IO protocol", () => {
    it("should ignore HTTP requests with same sid after upgrade", async () => {
      const sid = await initLongPollingSession();

-      const socket = new WebSocket(
+      const socket = createWebSocket(
        `${WS_URL}/socket.io/?EIO=4&transport=websocket&sid=${sid}`
      );

      await waitFor(socket, "open");
      socket.send("2probe");
+      await waitFor(socket, "message"); // "3probe"
      socket.send("5");

      const pollResponse = await fetch(
@@ -371,15 +391,16 @@ describe("Engine.IO protocol", () => {
    it("should ignore WebSocket connection with same sid after upgrade", async () => {
      const sid = await initLongPollingSession();

-      const socket = new WebSocket(
+      const socket = createWebSocket(
        `${WS_URL}/socket.io/?EIO=4&transport=websocket&sid=${sid}`
      );

      await waitFor(socket, "open");
      socket.send("2probe");
+      await waitFor(socket, "message"); // "3probe"
      socket.send("5");

-      const socket2 = new WebSocket(
+      const socket2 = createWebSocket(
        `${WS_URL}/socket.io/?EIO=4&transport=websocket&sid=${sid}`
      );

@@ -391,7 +412,7 @@ describe("Engine.IO protocol", () => {
 describe("Socket.IO protocol", () => {
  describe("connect", () => {
    it("should allow connection to the main namespace", async () => {
-      const socket = new WebSocket(
+      const socket = createWebSocket(
        `${WS_URL}/socket.io/?EIO=4&transport=websocket`
      );

@@ -414,7 +435,7 @@ describe("Socket.IO protocol", () => {
    });

    it("should allow connection to the main namespace with a payload", async () => {
-      const socket = new WebSocket(
+      const socket = createWebSocket(
        `${WS_URL}/socket.io/?EIO=4&transport=websocket`
      );

@@ -437,7 +458,7 @@ describe("Socket.IO protocol", () => {
    });

    it("should allow connection to a custom namespace", async () => {
-      const socket = new WebSocket(
+      const socket = createWebSocket(
        `${WS_URL}/socket.io/?EIO=4&transport=websocket`
      );

@@ -460,7 +481,7 @@ describe("Socket.IO protocol", () => {
    });

    it("should allow connection to a custom namespace with a payload", async () => {
-      const socket = new WebSocket(
+      const socket = createWebSocket(
        `${WS_URL}/socket.io/?EIO=4&transport=websocket`
      );

@@ -483,7 +504,7 @@ describe("Socket.IO protocol", () => {
    });

    it("should disallow connection to an unknown namespace", async () => {
-      const socket = new WebSocket(
+      const socket = createWebSocket(
        `${WS_URL}/socket.io/?EIO=4&transport=websocket`
      );

@@ -497,7 +518,7 @@ describe("Socket.IO protocol", () => {
    });

    it("should disallow connection with an invalid handshake", async () => {
-      const socket = new WebSocket(
+      const socket = createWebSocket(
        `${WS_URL}/socket.io/?EIO=4&transport=websocket`
      );

@@ -508,10 +529,9 @@ describe("Socket.IO protocol", () => {
      await waitFor(socket, "close");
    });

-    
    it("should close the connection if no handshake is received", async () => {
-      const socket = new WebSocket(
-          `${WS_URL}/socket.io/?EIO=4&transport=websocket`
+      const socket = createWebSocket(
+        `${WS_URL}/socket.io/?EIO=4&transport=websocket`
      );

      await waitFor(socket, "close");
--- a/examples/basic-websocket-client/package.json
+++ b/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",
--- a/package-lock.json
+++ b/package-lock.json
--- a/package.json
+++ b/package.json
@@ -8,14 +8,16 @@
    "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",
+    "packages/socket.io-postgres-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",
@@ -29,10 +31,12 @@
    "@rollup/plugin-commonjs": "^26.0.1",
    "@rollup/plugin-node-resolve": "^15.2.3",
    "@sinonjs/fake-timers": "^11.2.2",
+    "@socket.io/postgres-adapter": "^0.1.0",
    "@types/debug": "^4.1.12",
    "@types/expect.js": "^0.3.32",
    "@types/mocha": "^10.0.7",
    "@types/node": "18.15.3",
+    "@types/pg": "^8.6.0",
    "@types/sinonjs__fake-timers": "^8.1.5",
    "@wdio/cli": "^8.39.1",
    "@wdio/local-runner": "^8.39.1",
@@ -43,6 +47,7 @@
    "base64-arraybuffer": "^1.0.2",
    "benchmark": "^2.1.4",
    "blob": "^0.1.0",
+    "cookie": "~0.7.2",
    "eiows": "^7.1.0",
    "engine.io-client-v3": "npm:engine.io-client@^3.5.2",
    "expect.js": "^0.3.1",
@@ -54,6 +59,7 @@
    "mocha": "^10.6.0",
    "node-forge": "^1.3.1",
    "nyc": "^17.0.0",
+    "pg": "^8.6.0",
    "prettier": "^3.3.2",
    "redis": "^4.6.15",
    "rimraf": "^6.0.0",
@@ -68,6 +74,7 @@
    "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"
--- a/packages/engine.io-client/lib/transport.ts
+++ b/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;
--- a/packages/engine.io-client/package.json
+++ b/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": {
--- a/packages/engine.io-client/test/transport.js
+++ b/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",
--- a/packages/engine.io-parser/lib/commons.ts
+++ b/packages/engine.io-parser/lib/commons.ts
@@ -32,7 +32,11 @@ export type RawData = any;

 export interface Packet {
  type: PacketType;
-  options?: { compress: boolean };
+  options?: {
+    compress: boolean;
+    wsPreEncoded?: string; // deprecated in favor of `wsPreEncodedFrame`
+    wsPreEncodedFrame?: any; // computed in the socket.io-adapter package (should be typed as Buffer)
+  };
  data?: RawData;
 }

--- a/packages/engine.io/CHANGELOG.md
+++ b/packages/engine.io/CHANGELOG.md
@@ -2,6 +2,7 @@

 | Version                                                                                              | Release date   |
 |------------------------------------------------------------------------------------------------------|----------------|
+| [6.6.4](#664-2025-01-28)                                                                             | January 2025   |
 | [6.6.3](#663-2025-01-23)                                                                             | January 2025   |
 | [6.6.2](#662-2024-10-09)                                                                             | October 2024   |
 | [6.6.1](#661-2024-09-21)                                                                             | September 2024 |
@@ -48,6 +49,17 @@

 # Release notes

+## [6.6.4](https://github.com/socketio/socket.io/compare/engine.io@6.6.3...engine.io@6.6.4) (2025-01-28)
+
+The bump of the `cookie` dependency was reverted, as it drops support for older Node.js versions (< 14).
+
+
+### Dependencies
+
+- [`ws@~8.17.1`](https://github.com/websockets/ws/releases/tag/8.17.1) (no change)
+
+
+
 ## [6.6.3](https://github.com/socketio/socket.io/compare/engine.io@6.6.2...engine.io@6.6.3) (2025-01-23)

 This release contains a bump of the `cookie` dependency.
--- a/packages/engine.io/lib/contrib/types.cookie.ts
+++ b/packages/engine.io/lib/contrib/types.cookie.ts
@@ -0,0 +1,117 @@
+// imported from https://github.com/DefinitelyTyped/DefinitelyTyped/blob/b83cf9ef8b044e69f05b2a00aa7c6cb767a9acd2/types/cookie/index.d.ts (now deleted)
+/**
+ * Basic HTTP cookie parser and serializer for HTTP servers.
+ */
+
+/**
+ * Additional serialization options
+ */
+export interface CookieSerializeOptions {
+  /**
+   * Specifies the value for the {@link https://tools.ietf.org/html/rfc6265#section-5.2.3|Domain Set-Cookie attribute}. By default, no
+   * domain is set, and most clients will consider the cookie to apply to only
+   * the current domain.
+   */
+  domain?: string | undefined;
+
+  /**
+   * Specifies a function that will be used to encode a cookie's value. Since
+   * value of a cookie has a limited character set (and must be a simple
+   * string), this function can be used to encode a value into a string suited
+   * for a cookie's value.
+   *
+   * The default function is the global `encodeURIComponent`, which will
+   * encode a JavaScript string into UTF-8 byte sequences and then URL-encode
+   * any that fall outside of the cookie range.
+   */
+  encode?(value: string): string;
+
+  /**
+   * Specifies the `Date` object to be the value for the {@link https://tools.ietf.org/html/rfc6265#section-5.2.1|`Expires` `Set-Cookie` attribute}. By default,
+   * no expiration is set, and most clients will consider this a "non-persistent cookie" and will delete
+   * it on a condition like exiting a web browser application.
+   *
+   * *Note* the {@link https://tools.ietf.org/html/rfc6265#section-5.3|cookie storage model specification}
+   * states that if both `expires` and `maxAge` are set, then `maxAge` takes precedence, but it is
+   * possible not all clients by obey this, so if both are set, they should
+   * point to the same date and time.
+   */
+  expires?: Date | undefined;
+  /**
+   * Specifies the boolean value for the {@link https://tools.ietf.org/html/rfc6265#section-5.2.6|`HttpOnly` `Set-Cookie` attribute}.
+   * When truthy, the `HttpOnly` attribute is set, otherwise it is not. By
+   * default, the `HttpOnly` attribute is not set.
+   *
+   * *Note* be careful when setting this to true, as compliant clients will
+   * not allow client-side JavaScript to see the cookie in `document.cookie`.
+   */
+  httpOnly?: boolean | undefined;
+  /**
+   * Specifies the number (in seconds) to be the value for the `Max-Age`
+   * `Set-Cookie` attribute. The given number will be converted to an integer
+   * by rounding down. By default, no maximum age is set.
+   *
+   * *Note* the {@link https://tools.ietf.org/html/rfc6265#section-5.3|cookie storage model specification}
+   * states that if both `expires` and `maxAge` are set, then `maxAge` takes precedence, but it is
+   * possible not all clients by obey this, so if both are set, they should
+   * point to the same date and time.
+   */
+  maxAge?: number | undefined;
+  /**
+   * Specifies the `boolean` value for the [`Partitioned` `Set-Cookie`](rfc-cutler-httpbis-partitioned-cookies)
+   * attribute. When truthy, the `Partitioned` attribute is set, otherwise it is not. By default, the
+   * `Partitioned` attribute is not set.
+   *
+   * **note** This is an attribute that has not yet been fully standardized, and may change in the future.
+   * This also means many clients may ignore this attribute until they understand it.
+   *
+   * More information about can be found in [the proposal](https://github.com/privacycg/CHIPS)
+   */
+  partitioned?: boolean | undefined;
+  /**
+   * Specifies the value for the {@link https://tools.ietf.org/html/rfc6265#section-5.2.4|`Path` `Set-Cookie` attribute}.
+   * By default, the path is considered the "default path".
+   */
+  path?: string | undefined;
+  /**
+   * Specifies the `string` to be the value for the [`Priority` `Set-Cookie` attribute][rfc-west-cookie-priority-00-4.1].
+   *
+   * - `'low'` will set the `Priority` attribute to `Low`.
+   * - `'medium'` will set the `Priority` attribute to `Medium`, the default priority when not set.
+   * - `'high'` will set the `Priority` attribute to `High`.
+   *
+   * More information about the different priority levels can be found in
+   * [the specification][rfc-west-cookie-priority-00-4.1].
+   *
+   * **note** This is an attribute that has not yet been fully standardized, and may change in the future.
+   * This also means many clients may ignore this attribute until they understand it.
+   */
+  priority?: "low" | "medium" | "high" | undefined;
+  /**
+   * Specifies the boolean or string to be the value for the {@link https://tools.ietf.org/html/draft-ietf-httpbis-rfc6265bis-03#section-4.1.2.7|`SameSite` `Set-Cookie` attribute}.
+   *
+   * - `true` will set the `SameSite` attribute to `Strict` for strict same
+   * site enforcement.
+   * - `false` will not set the `SameSite` attribute.
+   * - `'lax'` will set the `SameSite` attribute to Lax for lax same site
+   * enforcement.
+   * - `'strict'` will set the `SameSite` attribute to Strict for strict same
+   * site enforcement.
+   *  - `'none'` will set the SameSite attribute to None for an explicit
+   *  cross-site cookie.
+   *
+   * More information about the different enforcement levels can be found in {@link https://tools.ietf.org/html/draft-ietf-httpbis-rfc6265bis-03#section-4.1.2.7|the specification}.
+   *
+   * *note* This is an attribute that has not yet been fully standardized, and may change in the future. This also means many clients may ignore this attribute until they understand it.
+   */
+  sameSite?: true | false | "lax" | "strict" | "none" | undefined;
+  /**
+   * Specifies the boolean value for the {@link https://tools.ietf.org/html/rfc6265#section-5.2.5|`Secure` `Set-Cookie` attribute}. When truthy, the
+   * `Secure` attribute is set, otherwise it is not. By default, the `Secure` attribute is not set.
+   *
+   * *Note* be careful when setting this to `true`, as compliant clients will
+   * not send the cookie back to the server in the future if the browser does
+   * not have an HTTPS connection.
+   */
+  secure?: boolean | undefined;
+}
--- a/packages/engine.io/lib/engine.io.ts
+++ b/packages/engine.io/lib/engine.io.ts
@@ -1,27 +1,36 @@
-import { createServer } from "http";
+import { createServer, Server as HttpServer } from "http";
 import { Server, AttachOptions, ServerOptions } from "./server";
 import transports from "./transports/index";
 import * as parser from "engine.io-parser";

 export { Server, transports, listen, attach, parser };
-export type { AttachOptions, ServerOptions, BaseServer } from "./server";
+export type {
+  AttachOptions,
+  ServerOptions,
+  BaseServer,
+  ErrorCallback,
+} from "./server";
 export { uServer } from "./userver";
 export { Socket } from "./socket";
 export { Transport } from "./transport";
 export const protocol = parser.protocol;

 /**
- * Creates an http.Server exclusively used for WS upgrades.
+ * Creates an http.Server exclusively used for WS upgrades, and starts listening.
 *
- * @param {Number} port
- * @param {Function} callback
- * @param {Object} options
- * @return {Server} websocket.io server
+ * @param port
+ * @param options
+ * @param listenCallback - callback for http.Server.listen()
+ * @return engine.io server
 */

-function listen(port, options: AttachOptions & ServerOptions, fn) {
+function listen(
+  port: number,
+  options?: AttachOptions & ServerOptions,
+  listenCallback?: () => void,
+): Server {
  if ("function" === typeof options) {
-    fn = options;
+    listenCallback = options;
    options = {};
  }

@@ -34,7 +43,7 @@ function listen(port, options: AttachOptions & ServerOptions, fn) {
  const engine = attach(server, options);
  engine.httpServer = server;

-  server.listen(port, fn);
+  server.listen(port, listenCallback);

  return engine;
 }
@@ -42,12 +51,15 @@ function listen(port, options: AttachOptions & ServerOptions, fn) {
 /**
 * Captures upgrade requests for a http.Server.
 *
- * @param {http.Server} server
- * @param {Object} options
- * @return {Server} engine server
+ * @param server
+ * @param options
+ * @return engine.io server
 */

-function attach(server, options: AttachOptions & ServerOptions) {
+function attach(
+  server: HttpServer,
+  options: AttachOptions & ServerOptions,
+): Server {
  const engine = new Server(options);
  engine.attach(server, options);
  return engine;
--- a/packages/engine.io/lib/parser-v3/index.ts
+++ b/packages/engine.io/lib/parser-v3/index.ts
@@ -59,8 +59,7 @@ const EMPTY_BUFFER = Buffer.concat([]);
 *
 * @api private
 */
-
-export function encodePacket (packet, supportsBinary, utf8encode, callback) {
+export function encodePacket (packet: any, supportsBinary?: any, utf8encode?: any, callback?: any) {
  if (typeof supportsBinary === 'function') {
    callback = supportsBinary;
    supportsBinary = null;
@@ -86,7 +85,7 @@ export function encodePacket (packet, supportsBinary, utf8encode, callback) {
  }

  return callback('' + encoded);
-};
+}

 /**
 * Encode Buffer data
@@ -120,16 +119,16 @@ export function encodeBase64Packet (packet, callback){
 /**
 * Decodes a packet. Data also available as an ArrayBuffer if requested.
 *
- * @return {Object} with `type` and `data` (if any)
+ * @return {import('engine.io-parser').Packet} with `type` and `data` (if any)
 * @api private
 */

-export function decodePacket (data, binaryType, utf8decode) {
+export function decodePacket (data: any, binaryType?: any, utf8decode?: any): any {
  if (data === undefined) {
    return err;
  }

-  var type;
+  let type: string | number;

  // String data
  if (typeof data === 'string') {
@@ -147,6 +146,7 @@ export function decodePacket (data, binaryType, utf8decode) {
      }
    }

+    // @ts-expect-error
    if (Number(type) != type || !packetslist[type]) {
      return err;
    }
@@ -274,7 +274,7 @@ function map(ary, each, done) {
 * @api public
 */

-export function decodePayload (data, binaryType, callback) {
+export function decodePayload (data: any, binaryType?: any, callback?: any) {
  if (typeof data !== 'string') {
    return decodePayloadAsBinary(data, binaryType, callback);
  }
--- a/packages/engine.io/lib/server.ts
+++ b/packages/engine.io/lib/server.ts
@@ -6,8 +6,12 @@ import { EventEmitter } from "events";
 import { Socket } from "./socket";
 import debugModule from "debug";
 import { serialize } from "cookie";
-import type { SerializeOptions } from "cookie";
-import { Server as DEFAULT_WS_ENGINE } from "ws";
+import {
+  Server as DEFAULT_WS_ENGINE,
+  type Server as WsServer,
+  type PerMessageDeflateOptions,
+  type WebSocket as WsWebSocket,
+} from "ws";
 import type {
  IncomingMessage,
  Server as HttpServer,
@@ -17,13 +21,19 @@ import type { CorsOptions, CorsOptionsDelegate } from "cors";
 import type { Duplex } from "stream";
 import { WebTransport } from "./transports/webtransport";
 import { createPacketDecoderStream } from "engine.io-parser";
-import type { EngineRequest } from "./transport";
+import type { EngineRequest, Transport } from "./transport";
+import type { CookieSerializeOptions } from "./contrib/types.cookie";

 const debug = debugModule("engine");

 const kResponseHeaders = Symbol("responseHeaders");

-type Transport = "polling" | "websocket" | "webtransport";
+type TransportName = "polling" | "websocket" | "webtransport";
+
+export type ErrorCallback = (
+  errorCode?: (typeof Server.errors)[keyof typeof Server.errors],
+  errorContext?: Record<string, unknown> & { name?: string; message?: string },
+) => void;

 export interface AttachOptions {
  /**
@@ -90,7 +100,7 @@ export interface ServerOptions {
   *
   * @default ["polling", "websocket"]
   */
-  transports?: Transport[];
+  transports?: TransportName[];
  /**
   * whether to allow transport upgrades
   * @default true
@@ -100,7 +110,7 @@ export interface ServerOptions {
   * parameters of the WebSocket permessage-deflate extension (see ws module api docs). Set to false to disable.
   * @default false
   */
-  perMessageDeflate?: boolean | object;
+  perMessageDeflate?: boolean | PerMessageDeflateOptions;
  /**
   * parameters of the http compression for the polling transports (see zlib api docs). Set to false to disable.
   * @default true
@@ -123,7 +133,7 @@ export interface ServerOptions {
   * might be used for sticky-session. Defaults to not sending any cookie.
   * @default false
   */
-  cookie?: (SerializeOptions & { name: string }) | boolean;
+  cookie?: (CookieSerializeOptions & { name: string }) | boolean;
  /**
   * the options that will be forwarded to the cors module
   */
@@ -149,7 +159,7 @@ type Middleware = (
  next: (err?: any) => void,
 ) => void;

-function parseSessionId(data: string) {
+function parseSessionId(data: string): string | undefined {
  try {
    const parsed = JSON.parse(data);
    if (typeof parsed.sid === "string") {
@@ -224,7 +234,7 @@ export abstract class BaseServer extends EventEmitter {
    this.init();
  }

-  protected abstract init();
+  protected abstract init(): void;

  /**
   * Compute the pathname of the requests that are handled by the server
@@ -244,10 +254,8 @@ export abstract class BaseServer extends EventEmitter {

  /**
   * Returns a list of available transports for upgrade given a certain transport.
-   *
-   * @return {Array}
   */
-  public upgrades(transport: string) {
+  public upgrades(transport: TransportName): string[] {
    if (!this.opts.allowUpgrades) return [];
    return transports[transport].upgradesTo || [];
  }
@@ -259,17 +267,18 @@ export abstract class BaseServer extends EventEmitter {
   * @param upgrade - whether it's an upgrade request
   * @param fn
   * @protected
+   * @return whether the request is valid
   */
  protected verify(
-    req: any,
+    req: EngineRequest,
    upgrade: boolean,
-    fn: (errorCode?: number, errorContext?: any) => void,
-  ) {
+    fn: ErrorCallback,
+  ): void | boolean {
    // transport check
    const transport = req._query.transport;
    // WebTransport does not go through the verify() method, see the onWebTransportSession() method
    if (
-      !~this.opts.transports.indexOf(transport) ||
+      !~this.opts.transports.indexOf(transport as TransportName) ||
      transport === "webtransport"
    ) {
      debug('unknown transport "%s"', transport);
@@ -408,7 +417,7 @@ export abstract class BaseServer extends EventEmitter {
   *
   * @param {IncomingMessage} req - the request object
   */
-  public generateId(req: IncomingMessage) {
+  public generateId(req: IncomingMessage): string | PromiseLike<string> {
    return base64id.generateId();
  }

@@ -422,9 +431,9 @@ export abstract class BaseServer extends EventEmitter {
   * @protected
   */
  protected async handshake(
-    transportName: string,
-    req: any,
-    closeConnection: (errorCode?: number, errorContext?: any) => void,
+    transportName: TransportName,
+    req: EngineRequest,
+    closeConnection: ErrorCallback,
  ) {
    const protocol = req._query.EIO === "4" ? 4 : 3; // 3rd revision by default
    if (protocol === 3 && !this.opts.allowEIO3) {
@@ -600,7 +609,10 @@ export abstract class BaseServer extends EventEmitter {
    }
  }

-  protected abstract createTransport(transportName, req);
+  protected abstract createTransport(
+    transportName: TransportName,
+    req: EngineRequest,
+  );

  /**
   * Protocol errors mappings.
@@ -613,7 +625,7 @@ export abstract class BaseServer extends EventEmitter {
    BAD_REQUEST: 3,
    FORBIDDEN: 4,
    UNSUPPORTED_PROTOCOL_VERSION: 5,
-  };
+  } as const;

  static errorMessages = {
    0: "Transport unknown",
@@ -622,7 +634,7 @@ export abstract class BaseServer extends EventEmitter {
    3: "Bad request",
    4: "Forbidden",
    5: "Unsupported protocol version",
-  };
+  } as const;
 }

 /**
@@ -667,7 +679,7 @@ class WebSocketResponse {
 */
 export class Server extends BaseServer {
  public httpServer?: HttpServer;
-  private ws: any;
+  private ws: WsServer;

  /**
   * Initialize websocket server
@@ -687,7 +699,7 @@ export class Server extends BaseServer {
    });

    if (typeof this.ws.on === "function") {
-      this.ws.on("headers", (headersArray, req) => {
+      this.ws.on("headers", (headersArray, req: EngineRequest) => {
        // note: 'ws' uses an array of headers, while Engine.IO uses an object (response.writeHead() accepts both formats)
        // we could also try to parse the array and then sync the values, but that will be error-prone
        const additionalHeaders = req[kResponseHeaders] || {};
@@ -730,7 +742,11 @@ export class Server extends BaseServer {
    }
  }

-  protected createTransport(transportName: string, req: IncomingMessage) {
+  protected createTransport(
+    transportName: TransportName,
+    req: IncomingMessage,
+  ): Transport {
+    // @ts-expect-error 'polling' is a plain function used as constructor
    return new transports[transportName](req);
  }

@@ -745,7 +761,7 @@ export class Server extends BaseServer {
    this.prepare(req);
    req.res = res;

-    const callback = (errorCode, errorContext) => {
+    const callback: ErrorCallback = (errorCode, errorContext) => {
      if (errorCode !== undefined) {
        this.emit("connection_error", {
          req,
@@ -763,7 +779,11 @@ export class Server extends BaseServer {
      } else {
        const closeConnection = (errorCode, errorContext) =>
          abortRequest(res, errorCode, errorContext);
-        this.handshake(req._query.transport, req, closeConnection);
+        this.handshake(
+          req._query.transport as TransportName,
+          req,
+          closeConnection,
+        );
      }
    };

@@ -787,7 +807,7 @@ export class Server extends BaseServer {
    this.prepare(req);

    const res = new WebSocketResponse(req, socket);
-    const callback = (errorCode, errorContext) => {
+    const callback: ErrorCallback = (errorCode, errorContext) => {
      if (errorCode !== undefined) {
        this.emit("connection_error", {
          req,
@@ -823,11 +843,16 @@ export class Server extends BaseServer {

  /**
   * Called upon a ws.io connection.
-   *
-   * @param {ws.Socket} websocket
+   * @param req
+   * @param socket
+   * @param websocket
   * @private
   */
-  private onWebSocket(req, socket, websocket) {
+  private onWebSocket(
+    req: EngineRequest,
+    socket: Duplex,
+    websocket: WsWebSocket,
+  ) {
    websocket.on("error", onUpgradeError);

    if (
@@ -862,14 +887,22 @@ export class Server extends BaseServer {
        // transport error handling takes over
        websocket.removeListener("error", onUpgradeError);

-        const transport = this.createTransport(req._query.transport, req);
+        const transport = this.createTransport(
+          req._query.transport as TransportName,
+          req,
+        );
+        // @ts-expect-error this option is only for WebSocket impl
        transport.perMessageDeflate = this.opts.perMessageDeflate;
        client._maybeUpgrade(transport);
      }
    } else {
      const closeConnection = (errorCode, errorContext) =>
        abortUpgrade(socket, errorCode, errorContext);
-      this.handshake(req._query.transport, req, closeConnection);
+      this.handshake(
+        req._query.transport as TransportName,
+        req,
+        closeConnection,
+      );
    }

    function onUpgradeError() {
@@ -947,7 +980,11 @@ export class Server extends BaseServer {
 * @private
 */

-function abortRequest(res, errorCode, errorContext) {
+function abortRequest(
+  res: ServerResponse,
+  errorCode: number,
+  errorContext?: { message?: string },
+) {
  const statusCode = errorCode === Server.errors.FORBIDDEN ? 403 : 400;
  const message =
    errorContext && errorContext.message
@@ -1030,7 +1067,7 @@ const validHdrChars = [
  1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1  // ... 255
 ]

-function checkInvalidHeaderChar(val) {
+function checkInvalidHeaderChar(val?: string) {
  val += "";
  if (val.length < 1) return false;
  if (!validHdrChars[val.charCodeAt(0)]) {
--- a/packages/engine.io/lib/socket.ts
+++ b/packages/engine.io/lib/socket.ts
@@ -5,6 +5,7 @@ import type { EngineRequest, Transport } from "./transport";
 import type { BaseServer } from "./server";
 import { setTimeout, clearTimeout } from "timers";
 import type { Packet, PacketType, RawData } from "engine.io-parser";
+import type transports from "./transports";

 const debug = debugModule("engine:socket");

@@ -537,9 +538,11 @@ export class Socket extends EventEmitter {
   */
  private getAvailableUpgrades() {
    const availableUpgrades = [];
-    const allUpgrades = this.server.upgrades(this.transport.name);
+    const allUpgrades = this.server.upgrades(
+      this.transport.name as keyof typeof transports,
+    );
    for (let i = 0; i < allUpgrades.length; ++i) {
-      const upg = allUpgrades[i];
+      const upg = allUpgrades[i] as keyof typeof transports;
      if (this.server.opts.transports.indexOf(upg) !== -1) {
        availableUpgrades.push(upg);
      }
--- a/packages/engine.io/lib/transport.ts
+++ b/packages/engine.io/lib/transport.ts
@@ -4,6 +4,7 @@ import * as parser_v3 from "./parser-v3/index";
 import debugModule from "debug";
 import type { IncomingMessage, ServerResponse } from "http";
 import { Packet, RawData } from "engine.io-parser";
+import type { WebSocket } from "ws";

 const debug = debugModule("engine:transport");

@@ -15,7 +16,11 @@ export type EngineRequest = IncomingMessage & {
  _query: Record<string, string>;
  res?: ServerResponse;
  cleanup?: Function;
-  websocket?: any;
+  websocket?: WebSocket & {
+    _socket?: {
+      remoteAddress: string;
+    };
+  };
 };

 export abstract class Transport extends EventEmitter {
@@ -37,7 +42,7 @@ export abstract class Transport extends EventEmitter {
   *
   * @see https://github.com/socketio/engine.io-protocol
   */
-  public protocol: number;
+  public protocol: 3 | 4;

  /**
   * The current state of the transport.
@@ -53,7 +58,7 @@ export abstract class Transport extends EventEmitter {
   * The parser to use (depends on the revision of the {@link Transport#protocol}.
   * @protected
   */
-  protected parser: any;
+  protected parser: typeof parser_v4 | typeof parser_v3;
  /**
   * Whether the transport supports binary payloads (else it will be base64-encoded)
   * @protected
@@ -74,6 +79,11 @@ export abstract class Transport extends EventEmitter {
    this._readyState = state;
  }

+  /**
+   * The list of transports this transport can be upgraded to.
+   */
+  static upgradesTo: string[] = [];
+
  /**
   * Transport constructor.
   *
@@ -148,7 +158,7 @@ export abstract class Transport extends EventEmitter {
  /**
   * Called with the encoded packet data.
   *
-   * @param {String} data
+   * @param data
   * @protected
   */
  protected onData(data: RawData) {
--- a/packages/engine.io/lib/transports-uws/polling.ts
+++ b/packages/engine.io/lib/transports-uws/polling.ts
@@ -3,6 +3,8 @@ import { createGzip, createDeflate } from "zlib";
 import * as accepts from "accepts";
 import debugModule from "debug";
 import { HttpRequest, HttpResponse } from "uWebSockets.js";
+import type * as parser_v4 from "engine.io-parser";
+import type * as parser_v3 from "../parser-v3/index";

 const debug = debugModule("engine:polling");

@@ -228,9 +230,9 @@ export class Polling extends Transport {
    };

    if (this.protocol === 3) {
-      this.parser.decodePayload(data, callback);
+      (this.parser as typeof parser_v3).decodePayload(data, callback);
    } else {
-      this.parser.decodePayload(data).forEach(callback);
+      (this.parser as typeof parser_v4).decodePayload(data).forEach(callback);
    }
  }

@@ -263,7 +265,7 @@ export class Polling extends Transport {
      this.shouldClose = null;
    }

-    const doWrite = (data) => {
+    const doWrite = (data: string) => {
      const compress = packets.some((packet) => {
        return packet.options && packet.options.compress;
      });
@@ -271,9 +273,13 @@ export class Polling extends Transport {
    };

    if (this.protocol === 3) {
-      this.parser.encodePayload(packets, this.supportsBinary, doWrite);
+      (this.parser as typeof parser_v3).encodePayload(
+        packets,
+        this.supportsBinary,
+        doWrite,
+      );
    } else {
-      this.parser.encodePayload(packets, doWrite);
+      (this.parser as typeof parser_v4).encodePayload(packets, doWrite);
    }
  }

--- a/packages/engine.io/lib/transports/index.ts
+++ b/packages/engine.io/lib/transports/index.ts
@@ -2,9 +2,10 @@ import { Polling as XHR } from "./polling";
 import { JSONP } from "./polling-jsonp";
 import { WebSocket } from "./websocket";
 import { WebTransport } from "./webtransport";
+import type { EngineRequest } from "../transport";

 export default {
-  polling: polling,
+  polling,
  websocket: WebSocket,
  webtransport: WebTransport,
 };
@@ -12,8 +13,7 @@ export default {
 /**
 * Polling polymorphic constructor.
 */
-
-function polling(req) {
+function polling(req: EngineRequest) {
  if ("string" === typeof req._query.j) {
    return new JSONP(req);
  } else {
--- a/packages/engine.io/lib/transports/polling.ts
+++ b/packages/engine.io/lib/transports/polling.ts
@@ -4,6 +4,8 @@ import * as accepts from "accepts";
 import debugModule from "debug";
 import type { IncomingMessage, ServerResponse } from "http";
 import type { Packet, RawData } from "engine.io-parser";
+import type * as parser_v4 from "engine.io-parser";
+import type * as parser_v3 from "../parser-v3/index";

 const debug = debugModule("engine:polling");

@@ -196,9 +198,9 @@ export class Polling extends Transport {
    };

    if (this.protocol === 3) {
-      this.parser.decodePayload(data, callback);
+      (this.parser as typeof parser_v3).decodePayload(data, callback);
    } else {
-      this.parser.decodePayload(data).forEach(callback);
+      (this.parser as typeof parser_v4).decodePayload(data).forEach(callback);
    }
  }

@@ -225,7 +227,7 @@ export class Polling extends Transport {
      this.shouldClose = null;
    }

-    const doWrite = (data) => {
+    const doWrite = (data: string) => {
      const compress = packets.some((packet) => {
        return packet.options && packet.options.compress;
      });
@@ -233,9 +235,13 @@ export class Polling extends Transport {
    };

    if (this.protocol === 3) {
-      this.parser.encodePayload(packets, this.supportsBinary, doWrite);
+      (this.parser as typeof parser_v3).encodePayload(
+        packets,
+        this.supportsBinary,
+        doWrite,
+      );
    } else {
-      this.parser.encodePayload(packets, doWrite);
+      (this.parser as typeof parser_v4).encodePayload(packets, doWrite);
    }
  }

--- a/packages/engine.io/lib/transports/websocket.ts
+++ b/packages/engine.io/lib/transports/websocket.ts
@@ -1,12 +1,13 @@
 import { EngineRequest, Transport } from "../transport";
 import debugModule from "debug";
 import type { Packet, RawData } from "engine.io-parser";
+import type { PerMessageDeflateOptions, WebSocket as WsWebSocket } from "ws";

 const debug = debugModule("engine:ws");

 export class WebSocket extends Transport {
-  protected perMessageDeflate: any;
-  private socket: any;
+  perMessageDeflate?: boolean | PerMessageDeflateOptions;
+  private socket: WsWebSocket;

  /**
   * WebSocket transport
@@ -51,8 +52,8 @@ export class WebSocket extends Transport {
      if (this._canSendPreEncodedFrame(packet)) {
        // the WebSocket frame was computed with WebSocket.Sender.frame()
        // see https://github.com/websockets/ws/issues/617#issuecomment-283002469
+        // @ts-expect-error use of untyped member
        this.socket._sender.sendFrame(
-          // @ts-ignore
          packet.options.wsPreEncodedFrame,
          isLast ? this._onSentLast : this._onSent,
        );
@@ -74,8 +75,8 @@ export class WebSocket extends Transport {
  private _canSendPreEncodedFrame(packet: Packet) {
    return (
      !this.perMessageDeflate &&
+      // @ts-expect-error use of untyped member
      typeof this.socket?._sender?.sendFrame === "function" &&
-      // @ts-ignore
      packet.options?.wsPreEncodedFrame !== undefined
    );
  }
--- a/packages/engine.io/lib/userver.ts
+++ b/packages/engine.io/lib/userver.ts
@@ -2,6 +2,7 @@ import debugModule from "debug";
 import { AttachOptions, BaseServer, Server } from "./server";
 import { HttpRequest, HttpResponse, TemplatedApp } from "uWebSockets.js";
 import transports from "./transports-uws";
+import { EngineRequest } from "./transport";

 const debug = debugModule("engine:uws");

@@ -36,7 +37,7 @@ export class uServer extends BaseServer {
   *
   * @private
   */
-  private prepare(req, res: HttpResponse) {
+  private prepare(req: HttpRequest & EngineRequest, res: HttpResponse) {
    req.method = req.getMethod().toUpperCase();
    req.url = req.getUrl();

@@ -48,6 +49,7 @@ export class uServer extends BaseServer {
      req.headers[key] = value;
    });

+    // @ts-expect-error
    req.connection = {
      remoteAddress: Buffer.from(res.getRemoteAddressAsText()).toString(),
    };
@@ -57,7 +59,7 @@ export class uServer extends BaseServer {
    });
  }

-  protected createTransport(transportName, req) {
+  protected createTransport(transportName: string, req: EngineRequest) {
    return new transports[transportName](req);
  }

@@ -123,7 +125,7 @@ export class uServer extends BaseServer {
    req: HttpRequest & { res: any; _query: any },
  ) {
    debug('handling "%s" http request "%s"', req.getMethod(), req.getUrl());
-    this.prepare(req, res);
+    this.prepare(req as unknown as HttpRequest & EngineRequest, res);

    req.res = res;

@@ -146,7 +148,11 @@ export class uServer extends BaseServer {
      } else {
        const closeConnection = (errorCode, errorContext) =>
          this.abortRequest(res, errorCode, errorContext);
-        this.handshake(req._query.transport, req, closeConnection);
+        this.handshake(
+          req._query.transport,
+          req as unknown as EngineRequest,
+          closeConnection,
+        );
      }
    };

@@ -154,7 +160,11 @@ export class uServer extends BaseServer {
      if (err) {
        callback(Server.errors.BAD_REQUEST, { name: "MIDDLEWARE_FAILURE" });
      } else {
-        this.verify(req, false, callback);
+        this.verify(
+          req as unknown as HttpRequest & EngineRequest,
+          false,
+          callback,
+        );
      }
    });
  }
@@ -166,7 +176,7 @@ export class uServer extends BaseServer {
  ) {
    debug("on upgrade");

-    this.prepare(req, res);
+    this.prepare(req as unknown as HttpRequest & EngineRequest, res);

    req.res = res;

@@ -198,13 +208,16 @@ export class uServer extends BaseServer {
          return res.close();
        } else {
          debug("upgrading existing transport");
-          transport = this.createTransport(req._query.transport, req);
+          transport = this.createTransport(
+            req._query.transport,
+            req as unknown as EngineRequest,
+          );
          client._maybeUpgrade(transport);
        }
      } else {
        transport = await this.handshake(
          req._query.transport,
-          req,
+          req as unknown as EngineRequest,
          (errorCode, errorContext) =>
            this.abortRequest(res, errorCode, errorContext),
        );
@@ -231,15 +244,15 @@ export class uServer extends BaseServer {
      if (err) {
        callback(Server.errors.BAD_REQUEST, { name: "MIDDLEWARE_FAILURE" });
      } else {
-        this.verify(req, true, callback);
+        this.verify(req as unknown as EngineRequest, true, callback);
      }
    });
  }

  private abortRequest(
    res: HttpResponse | ResponseWrapper,
-    errorCode,
-    errorContext,
+    errorCode: number,
+    errorContext?: { message?: string },
  ) {
    const statusCode =
      errorCode === Server.errors.FORBIDDEN
--- a/packages/engine.io/package.json
+++ b/packages/engine.io/package.json
@@ -1,6 +1,6 @@
 {
  "name": "engine.io",
-  "version": "6.6.3",
+  "version": "6.6.4",
  "description": "The realtime engine behind Socket.IO. Provides the foundation of a bidirectional connection between client and server",
  "type": "commonjs",
  "main": "./build/engine.io.js",
@@ -35,11 +35,11 @@
    "@types/node": ">=10.0.0",
    "accepts": "~1.3.4",
    "base64id": "2.0.0",
-    "cookie": "~1.0.2",
+    "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",
--- a/packages/socket.io-adapter/lib/in-memory-adapter.ts
+++ b/packages/socket.io-adapter/lib/in-memory-adapter.ts
@@ -1,6 +1,6 @@
 import { EventEmitter } from "events";
 import { yeast } from "./contrib/yeast";
-import WebSocket = require("ws");
+import * as WebSocket from "ws";

 // @ts-expect-error
 const canPreComputeFrame = typeof WebSocket?.Sender?.frame === "function";
@@ -51,11 +51,11 @@ export class Adapter extends EventEmitter {
  /**
   * In-memory adapter constructor.
   *
-   * @param {Namespace} nsp
+   * @param nsp
   */
  constructor(readonly nsp: any) {
    super();
-    this.encoder = nsp.server.encoder;
+    this.encoder = nsp.server.encoder; // nsp is a Namespace object
  }

  /**
--- a/packages/socket.io-adapter/package.json
+++ b/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",
--- a/packages/socket.io-client/package.json
+++ b/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"
  },
--- a/packages/socket.io-client/wdio.conf.js
+++ b/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,
    },
    {
--- a/packages/socket.io-cluster-adapter/CHANGELOG.md
+++ b/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
+
--- a/packages/socket.io-cluster-adapter/LICENSE
+++ b/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.
--- a/packages/socket.io-cluster-adapter/README.md
+++ b/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)
--- a/packages/socket.io-cluster-adapter/assets/adapter.excalidraw
+++ b/packages/socket.io-cluster-adapter/assets/adapter.excalidraw
@@ -0,0 +1,822 @@
+{
+  "type": "excalidraw",
+  "version": 2,
+  "source": "https://excalidraw.com",
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+      "seed": 28708370,
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+      "boundElementIds": [
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+      "fontSize": 20,
+      "fontFamily": 1,
+      "text": "worker 1",
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+      "textAlign": "center",
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--- a/packages/socket.io-cluster-adapter/assets/adapter.png
+++ b/packages/socket.io-cluster-adapter/assets/adapter.png
--- a/packages/socket.io-cluster-adapter/lib/index.ts
+++ b/packages/socket.io-cluster-adapter/lib/index.ts
@@ -0,0 +1,116 @@
+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);
+          }
+        }
+    }
+  });
+}
--- a/packages/socket.io-cluster-adapter/package-lock.json
+++ b/packages/socket.io-cluster-adapter/package-lock.json
--- a/packages/socket.io-cluster-adapter/package.json
+++ b/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"
+  ]
+}
--- a/packages/socket.io-cluster-adapter/test/index.ts
+++ b/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();
+        }
+      });
+    });
+  });
+});
--- a/packages/socket.io-cluster-adapter/test/util.ts
+++ b/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));
+}
--- a/packages/socket.io-cluster-adapter/test/worker.js
+++ b/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));
--- a/packages/socket.io-cluster-adapter/tsconfig.json
+++ b/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/**/*"
+  ]
+}
--- a/packages/socket.io-cluster-engine/lib/engine.ts
+++ b/packages/socket.io-cluster-engine/lib/engine.ts
@@ -1,4 +1,10 @@
-import { Server, type ServerOptions, Socket, type Transport } from "engine.io";
+import {
+  Server,
+  type ServerOptions,
+  type ErrorCallback,
+  Socket,
+  type Transport,
+} from "engine.io";
 import { randomBytes } from "node:crypto";
 import { setTimeout, clearTimeout } from "node:timers";
 import { type IncomingMessage } from "node:http";
@@ -392,9 +398,9 @@ export abstract class ClusterEngine extends Server {
  override verify(
    req: IncomingMessage & { _query: Record<string, string> },
    upgrade: boolean,
-    fn: (errorCode?: number, context?: any) => void,
+    fn: ErrorCallback,
  ): void {
-    super.verify(req, upgrade, (errorCode: number, errorContext: any) => {
+    super.verify(req, upgrade, (errorCode, errorContext) => {
      if (errorCode !== Server.errors.UNKNOWN_SID) {
        return fn(errorCode, errorContext);
      }
@@ -412,7 +418,7 @@ export abstract class ClusterEngine extends Server {
          req[kSenderId] = senderId;
          fn();
        } else {
-          const transport = this.createTransport(transportName, req);
+          const transport = this.createTransport(transportName as any, req);
          this._hookTransport(sid, transport, lockType, senderId);
          transport.onRequest(req);
        }
--- a/packages/socket.io-cluster-engine/package.json
+++ b/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"
  },
--- a/packages/socket.io-parser/package.json
+++ b/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",
--- a/packages/socket.io-parser/wdio.conf.js
+++ b/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,
    },
    {
--- a/packages/socket.io-postgres-emitter/CHANGELOG.md
+++ b/packages/socket.io-postgres-emitter/CHANGELOG.md
@@ -0,0 +1,19 @@
+# History
+
+| Version                  | Release date   |
+|--------------------------|----------------|
+| [0.1.1](#011-2025-09-05) | September 2025 |
+| [0.1.0](#010-2021-06-14) | June 2021      |
+
+# Release notes
+
+## 0.1.1 (2025-09-05)
+
+### Bug Fixes
+
+* use parameterized query to send the NOTIFY command ([32257b6](https://github.com/socketio/socket.io/commit/32257b6cb89f9dac15e69e1d6ee76365ff262170))
+
+
+## 0.1.0 (2021-06-14)
+
+Initial release!
--- a/packages/socket.io-postgres-emitter/LICENSE
+++ b/packages/socket.io-postgres-emitter/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.
--- a/packages/socket.io-postgres-emitter/README.md
+++ b/packages/socket.io-postgres-emitter/README.md
@@ -0,0 +1,152 @@
+# Socket.IO Postgres emitter
+
+The `@socket.io/postgres-emitter` package allows you to easily communicate with a group of Socket.IO servers from another Node.js process (server-side).
+
+<picture>
+  <source media="(prefers-color-scheme: dark)" srcset="./assets/emitter_dark.png">
+  <img alt="Diagram of Socket.IO packets forwarded through PostgreSQL" src="./assets/emitter.png">
+</picture>
+
+It must be used in conjunction with [`@socket.io/postgres-adapter`](https://github.com/socketio/socket.io-postgres-adapter/).
+
+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)
+  - [`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/
+- Redis emitter: https://github.com/socketio/socket.io-redis-emitter/
+- MongoDB adapter: https://github.com/socketio/socket.io-mongo-adapter/
+- MongoDB emitter: https://github.com/socketio/socket.io-mongo-emitter/
+
+**Table of contents**
+
+- [Installation](#installation)
+- [Usage](#usage)
+- [API](#api)
+- [Known errors](#known-errors)
+- [License](#license)
+
+## Installation
+
+```
+npm install @socket.io/postgres-emitter pg
+```
+
+For TypeScript users, you might also need `@types/pg`.
+
+## Usage
+
+```js
+const { Emitter } = require("@socket.io/postgres-emitter");
+const { Pool } = require("pg");
+
+const pool = new Pool({
+  user: "postgres",
+  host: "localhost",
+  database: "postgres",
+  password: "changeit",
+  port: 5432,
+});
+
+const io = new Emitter(pool);
+
+setInterval(() => {
+  io.emit("ping", new Date());
+}, 1000);
+```
+
+## API
+
+### `Emitter(pool[, nsp][, opts])`
+
+```js
+const io = new Emitter(pool);
+```
+
+The `pool` argument is a [Pool object](https://node-postgres.com/api/pool) from the `pg` package.
+
+### `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)
--- a/packages/socket.io-postgres-emitter/assets/emitter.excalidraw
+++ b/packages/socket.io-postgres-emitter/assets/emitter.excalidraw
--- a/packages/socket.io-postgres-emitter/assets/emitter.png
+++ b/packages/socket.io-postgres-emitter/assets/emitter.png
--- a/packages/socket.io-postgres-emitter/assets/emitter_dark.png
+++ b/packages/socket.io-postgres-emitter/assets/emitter_dark.png
--- a/packages/socket.io-postgres-emitter/compose.yaml
+++ b/packages/socket.io-postgres-emitter/compose.yaml
@@ -0,0 +1,7 @@
+services:
+  postgres:
+    image: postgres:14
+    ports:
+      - "5432:5432"
+    environment:
+      POSTGRES_PASSWORD: "changeit"
--- a/packages/socket.io-postgres-emitter/lib/index.ts
+++ b/packages/socket.io-postgres-emitter/lib/index.ts
@@ -0,0 +1,536 @@
+import debugModule from "debug";
+import type {
+  DefaultEventsMap,
+  EventNames,
+  EventParams,
+  EventsMap,
+  TypedEventBroadcaster,
+} from "./typed-events";
+import { encode } from "@msgpack/msgpack";
+
+const debug = debugModule("socket.io-postgres-emitter");
+const EMITTER_UID = "emitter";
+
+const 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;
+};
+
+/**
+ * Event types, for messages between nodes
+ */
+
+enum EventType {
+  INITIAL_HEARTBEAT = 1,
+  HEARTBEAT,
+  BROADCAST,
+  SOCKETS_JOIN,
+  SOCKETS_LEAVE,
+  DISCONNECT_SOCKETS,
+  FETCH_SOCKETS,
+  FETCH_SOCKETS_RESPONSE,
+  SERVER_SIDE_EMIT,
+  SERVER_SIDE_EMIT_RESPONSE,
+}
+
+interface BroadcastFlags {
+  volatile?: boolean;
+  compress?: boolean;
+}
+
+export interface PostgresEmitterOptions {
+  /**
+   * The prefix of the notification channel
+   * @default "socket.io"
+   */
+  channelPrefix: string;
+  /**
+   * The name of the table for payloads over the 8000 bytes limit or containing binary data
+   */
+  tableName: string;
+  /**
+   * The threshold for the payload size in bytes (see https://www.postgresql.org/docs/current/sql-notify.html)
+   * @default 8000
+   */
+  payloadThreshold: number;
+}
+
+export class Emitter<
+  EmitEvents extends EventsMap = DefaultEventsMap,
+  ServerSideEvents extends EventsMap = DefaultEventsMap,
+> {
+  public readonly channel: string;
+  public readonly tableName: string;
+  public payloadThreshold: number;
+
+  constructor(
+    readonly pool: any,
+    readonly nsp: string = "/",
+    opts: Partial<PostgresEmitterOptions> = {},
+  ) {
+    const channelPrefix = opts.channelPrefix || "socket.io";
+    this.channel = `${channelPrefix}#${nsp}`;
+    this.tableName = opts.tableName || "socket_io_attachments";
+    this.payloadThreshold = opts.payloadThreshold || 8000;
+  }
+
+  /**
+   * Return a new emitter for the given namespace.
+   *
+   * @param nsp - namespace
+   * @public
+   */
+  public of(nsp: string): Emitter {
+    return new Emitter(this.pool, (nsp[0] !== "/" ? "/" : "") + nsp);
+  }
+
+  /**
+   * Emits to all clients.
+   *
+   * @return Always true
+   * @public
+   */
+  public emit<Ev extends EventNames<EmitEvents>>(
+    ev: Ev,
+    ...args: EventParams<EmitEvents, Ev>
+  ): true {
+    return new BroadcastOperator<EmitEvents, ServerSideEvents>(this).emit(
+      ev,
+      ...args,
+    );
+  }
+
+  /**
+   * Targets a room when emitting.
+   *
+   * @param room
+   * @return BroadcastOperator
+   * @public
+   */
+  public to(
+    room: string | string[],
+  ): BroadcastOperator<EmitEvents, ServerSideEvents> {
+    return new BroadcastOperator(this).to(room);
+  }
+
+  /**
+   * Targets a room when emitting.
+   *
+   * @param room
+   * @return BroadcastOperator
+   * @public
+   */
+  public in(
+    room: string | string[],
+  ): BroadcastOperator<EmitEvents, ServerSideEvents> {
+    return new BroadcastOperator(this).in(room);
+  }
+
+  /**
+   * Excludes a room when emitting.
+   *
+   * @param room
+   * @return BroadcastOperator
+   * @public
+   */
+  public except(
+    room: string | string[],
+  ): BroadcastOperator<EmitEvents, ServerSideEvents> {
+    return new BroadcastOperator(this).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 new BroadcastOperator(this).volatile;
+  }
+
+  /**
+   * Sets the compress flag.
+   *
+   * @param compress - if `true`, compresses the sending data
+   * @return BroadcastOperator
+   * @public
+   */
+  public compress(
+    compress: boolean,
+  ): BroadcastOperator<EmitEvents, ServerSideEvents> {
+    return new BroadcastOperator(this).compress(compress);
+  }
+
+  /**
+   * Makes the matching socket instances join the specified rooms
+   *
+   * @param rooms
+   * @public
+   */
+  public socketsJoin(rooms: string | string[]): void {
+    return new BroadcastOperator(this).socketsJoin(rooms);
+  }
+
+  /**
+   * Makes the matching socket instances leave the specified rooms
+   *
+   * @param rooms
+   * @public
+   */
+  public socketsLeave(rooms: string | string[]): void {
+    return new BroadcastOperator(this).socketsLeave(rooms);
+  }
+
+  /**
+   * Makes the matching socket instances disconnect
+   *
+   * @param close - whether to close the underlying connection
+   * @public
+   */
+  public disconnectSockets(close: boolean = false): void {
+    return new BroadcastOperator(this).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 new BroadcastOperator<EmitEvents, ServerSideEvents>(
+      this,
+    ).serverSideEmit(ev, ...args);
+  }
+}
+
+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 emitter: Emitter,
+    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.emitter,
+      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.emitter,
+      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.emitter,
+      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.emitter,
+      this.rooms,
+      this.exceptRooms,
+      flags,
+    );
+  }
+
+  private async publish(document: any) {
+    document.uid = EMITTER_UID;
+
+    try {
+      if (
+        [
+          EventType.BROADCAST,
+          EventType.SERVER_SIDE_EMIT,
+          EventType.SERVER_SIDE_EMIT_RESPONSE,
+        ].includes(document.type) &&
+        hasBinary(document)
+      ) {
+        return await this.publishWithAttachment(document);
+      }
+
+      const payload = JSON.stringify(document);
+      if (Buffer.byteLength(payload) > this.emitter.payloadThreshold) {
+        return await this.publishWithAttachment(document);
+      }
+
+      debug(
+        "sending event of type %s to channel %s",
+        document.type,
+        this.emitter.channel,
+      );
+      await this.emitter.pool.query("SELECT pg_notify($1, $2)", [
+        this.emitter.channel,
+        payload,
+      ]);
+    } catch (err) {
+      // @ts-ignore
+      this.emit("error", err);
+    }
+  }
+
+  private async publishWithAttachment(document: any) {
+    const payload = encode(document);
+
+    debug(
+      "sending event of type %s with attachment to channel %s",
+      document.type,
+      this.emitter.channel,
+    );
+    const result = await this.emitter.pool.query(
+      `INSERT INTO ${this.emitter.tableName} (payload) VALUES ($1) RETURNING id;`,
+      [payload],
+    );
+    const attachmentId = result.rows[0].id;
+    const headerPayload = JSON.stringify({
+      uid: document.uid,
+      type: document.type,
+      attachmentId,
+    });
+    await this.emitter.pool.query("SELECT pg_notify($1, $2)", [
+      this.emitter.channel,
+      headerPayload,
+    ]);
+  }
+
+  /**
+   * Emits to all clients.
+   *
+   * @return Always true
+   * @public
+   */
+  public emit<Ev extends EventNames<EmitEvents>>(
+    ev: Ev,
+    ...args: EventParams<EmitEvents, Ev>
+  ): true {
+    if (RESERVED_EVENTS.has(ev)) {
+      throw new Error(`"${String(ev)}" is a reserved event name`);
+    }
+
+    // set up packet object
+    const data = [ev, ...args];
+    const packet = {
+      type: 2, // EVENT
+      data: data,
+      nsp: this.emitter.nsp,
+    };
+
+    const opts = {
+      rooms: [...this.rooms],
+      flags: this.flags,
+      except: [...this.exceptRooms],
+    };
+
+    this.publish({
+      type: EventType.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: EventType.SOCKETS_JOIN,
+      data: {
+        opts: {
+          rooms: [...this.rooms],
+          except: [...this.exceptRooms],
+        },
+        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: EventType.SOCKETS_LEAVE,
+      data: {
+        opts: {
+          rooms: [...this.rooms],
+          except: [...this.exceptRooms],
+        },
+        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: EventType.DISCONNECT_SOCKETS,
+      data: {
+        opts: {
+          rooms: [...this.rooms],
+          except: [...this.exceptRooms],
+        },
+        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: EventType.SERVER_SIDE_EMIT,
+      data: {
+        packet: [ev, ...args],
+      },
+    });
+  }
+}
--- a/packages/socket.io-postgres-emitter/lib/typed-events.ts
+++ b/packages/socket.io-postgres-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;
+}
--- a/packages/socket.io-postgres-emitter/package.json
+++ b/packages/socket.io-postgres-emitter/package.json
@@ -0,0 +1,33 @@
+{
+  "name": "@socket.io/postgres-emitter",
+  "version": "0.1.1",
+  "description": "The Socket.IO Postgres 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-postgres-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",
+    "test": "npm run format:check && npm run compile && nyc mocha --require ts-node/register --timeout 5000 test/index.ts",
+    "format:check": "prettier --parser typescript --check 'lib/**/*.ts' 'test/**/*.ts'",
+    "format:fix": "prettier --parser typescript --write 'lib/**/*.ts' 'test/**/*.ts'",
+    "prepack": "npm run compile"
+  },
+  "dependencies": {
+    "@msgpack/msgpack": "^2.7.0",
+    "debug": "~4.4.1"
+  },
+  "keywords": [
+    "socket.io",
+    "postgres",
+    "postgresql",
+    "emitter"
+  ]
+}
--- a/packages/socket.io-postgres-emitter/test/index.ts
+++ b/packages/socket.io-postgres-emitter/test/index.ts
@@ -0,0 +1,278 @@
+import { createServer } from "http";
+import { Server, Socket as ServerSocket } from "socket.io";
+import { io as ioc, Socket as ClientSocket } from "socket.io-client";
+import expect = require("expect.js");
+import { createAdapter } from "@socket.io/postgres-adapter";
+import type { AddressInfo } from "net";
+import { Pool } from "pg";
+import { times, sleep } from "./util";
+import { Emitter } from "..";
+
+const NODES_COUNT = 3;
+
+describe("@socket.io/postgres-emitter", () => {
+  let servers: Server[],
+    serverSockets: ServerSocket[],
+    clientSockets: ClientSocket[],
+    pool: Pool,
+    emitter: Emitter;
+
+  beforeEach((done) => {
+    servers = [];
+    serverSockets = [];
+    clientSockets = [];
+    pool = new Pool({
+      user: "postgres",
+      host: "localhost",
+      database: "postgres",
+      password: "changeit",
+      port: 5432,
+    });
+
+    pool.query(
+      `
+      CREATE TABLE IF NOT EXISTS socket_io_attachments (
+          id          bigserial UNIQUE,
+          created_at  timestamptz DEFAULT NOW(),
+          payload     bytea
+      );
+    `,
+      () => {},
+    );
+
+    emitter = new Emitter(pool);
+
+    for (let i = 1; i <= NODES_COUNT; i++) {
+      const httpServer = createServer();
+      const io = new Server(httpServer);
+      // @ts-ignore
+      io.adapter(createAdapter(pool));
+      httpServer.listen(() => {
+        const port = (httpServer.address() as AddressInfo).port;
+        const clientSocket = ioc(`http://localhost:${port}`);
+
+        io.on("connection", async (socket) => {
+          clientSockets.push(clientSocket);
+          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");
+
+            await sleep(200);
+
+            done();
+          }
+        });
+      });
+    }
+  });
+
+  afterEach((done) => {
+    servers.forEach((server) => {
+      // @ts-ignore
+      server.httpServer.close();
+      server.of("/").adapter.close();
+    });
+    clientSockets.forEach((socket) => {
+      socket.disconnect();
+    });
+    pool.end(done);
+  });
+
+  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(200);
+
+        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(200);
+
+      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(200);
+
+      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(200);
+
+      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(200);
+
+      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(200);
+
+      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(200);
+
+      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();
+      });
+    });
+  });
+});
--- a/packages/socket.io-postgres-emitter/test/util.ts
+++ b/packages/socket.io-postgres-emitter/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));
+}
--- a/packages/socket.io-postgres-emitter/tsconfig.json
+++ b/packages/socket.io-postgres-emitter/tsconfig.json
@@ -0,0 +1,12 @@
+{
+  "compilerOptions": {
+    "outDir": "./dist",
+    "allowJs": false,
+    "target": "es2017",
+    "module": "commonjs",
+    "declaration": true
+  },
+  "include": [
+    "./lib/**/*"
+  ]
+}
--- a/packages/socket.io/lib/client.ts
+++ b/packages/socket.io/lib/client.ts
@@ -1,6 +1,6 @@
 import { Decoder, Encoder, Packet, PacketType } from "socket.io-parser";
-import debugModule = require("debug");
-import url = require("url");
+import debugModule from "debug";
+import url from "url";
 import type { IncomingMessage } from "http";
 import type { Server } from "./index";
 import type { Namespace } from "./namespace";
@@ -61,12 +61,13 @@ export class Client<
   */
  constructor(
    server: Server<ListenEvents, EmitEvents, ServerSideEvents, SocketData>,
-    conn: any,
+    conn: RawSocket,
  ) {
    this.server = server;
    this.conn = conn;
    this.encoder = server.encoder;
    this.decoder = new server._parser.Decoder();
+    // @ts-expect-error use of private
    this.id = conn.id;
    this.setup();
  }
@@ -216,13 +217,13 @@ export class Client<
   * @param {Object} opts
   * @private
   */
-  _packet(packet: Packet | any[], opts: WriteOptions = {}): void {
+  _packet(packet: Packet | Packet[], opts: WriteOptions = {}): void {
    if (this.conn.readyState !== "open") {
      debug("ignoring packet write %j", packet);
      return;
    }
    const encodedPackets = opts.preEncoded
-      ? (packet as any[]) // previous versions of the adapter incorrectly used socket.packet() instead of writeToEngine()
+      ? (packet as Packet[]) // previous versions of the adapter incorrectly used socket.packet() instead of writeToEngine()
      : this.encoder.encode(packet as Packet);
    this.writeToEngine(encodedPackets, opts);
  }
@@ -250,7 +251,7 @@ export class Client<
   *
   * @private
   */
-  private ondata(data): void {
+  private ondata(data: unknown): void {
    // try/catch is needed for protocol violations (GH-1880)
    try {
      this.decoder.add(data);
--- a/packages/socket.io/lib/index.ts
+++ b/packages/socket.io/lib/index.ts
@@ -1,4 +1,4 @@
-import http = require("http");
+import http from "http";
 import type { Server as HTTPSServer } from "https";
 import type { Http2SecureServer, Http2Server } from "http2";
 import { createReadStream } from "fs";
@@ -7,7 +7,11 @@ import accepts = require("accepts");
 import { pipeline } from "stream";
 import path = require("path");
 import { attach, Server as Engine, uServer } from "engine.io";
-import type { ServerOptions as EngineOptions, AttachOptions } from "engine.io";
+import type {
+  ServerOptions as EngineOptions,
+  AttachOptions,
+  Socket as RawSocket,
+} from "engine.io";
 import { Client } from "./client";
 import { EventEmitter } from "events";
 import { ExtendedError, Namespace, ServerReservedEventsMap } from "./namespace";
@@ -506,6 +510,11 @@ export class Server<
    return this;
  }

+  /**
+   * Attaches socket.io to a uWebSockets.js app.
+   * @param app
+   * @param opts
+   */
  public attachApp(app /*: TemplatedApp */, opts: Partial<ServerOptions> = {}) {
    // merge the options passed to the Socket.IO server
    Object.assign(opts, this.opts);
@@ -582,7 +591,7 @@ export class Server<
  ): void {
    // initialize engine
    debug("creating engine.io instance with opts %j", opts);
-    this.eio = attach(srv, opts);
+    this.eio = attach(srv as http.Server, opts);

    // attach static file serving
    if (this._serveClient) this.attachServe(srv);
@@ -723,11 +732,12 @@ export class Server<
   * @return self
   * @private
   */
-  private onconnection(conn): this {
+  private onconnection(conn: RawSocket): this {
+    // @ts-expect-error use of private
    debug("incoming connection with id %s", conn.id);
    const client = new Client(this, conn);
    if (conn.protocol === 3) {
-      // @ts-ignore
+      // @ts-expect-error use of private
      client.connect("/");
    }
    return this;
--- a/packages/socket.io/lib/namespace.ts
+++ b/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);
+    });
  }

  /**
--- a/packages/socket.io/lib/socket.ts
+++ b/packages/socket.io/lib/socket.ts
@@ -163,7 +163,7 @@ export class Socket<
  ) {
    super();
    this.server = nsp.server;
-    this.adapter = this.nsp.adapter;
+    this.adapter = nsp.adapter;
    if (previousSession) {
      this.id = previousSession.sid;
      this.pid = previousSession.pid;
--- a/packages/socket.io/package.json
+++ b/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"
Author	SHA1	Message	Date
Damien Arrachequesne	47ff1cd04c	chore(release): @socket.io/cluster-adapter@0.3.0 Diff: https://github.com/socketio/socket.io-cluster-adapter/compare/0.2.2...0.3.0	2025-10-16 19:55:56 +02:00
Damien Arrachequesne	0ae76360f9	Merge remote-tracking branch 'socket.io-cluster-adapter/monorepo'	2025-10-16 19:35:51 +02:00
Damien Arrachequesne	27fd420e75	refactor: prepare migration to monorepo	2025-10-16 19:31:30 +02:00
Damien Arrachequesne	0c431243e2	refactor: use the ClusterAdapter class from socket.io-adapter package The ClusterAdapter class has been moved to [1], so that this adapter only needs to implement to pub/sub mechanism. Also, [2] should reduce the number of "timeout reached: only x responses received out of y" errors, since the fetchSockets() requests will now succeed even if a server leaves the cluster. [1]: https://github.com/socketio/socket.io/tree/main/packages/socket.io-adapter [2]: `0e23ff0cc6`	2025-10-16 19:16:20 +02:00
Damien Arrachequesne	4fc25d80ec	ci: add Node.js 24 Reference: https://github.com/nodejs/Release	2025-10-16 12:03:32 +02:00
Damien Arrachequesne	1dd729b1a1	refactor: upgrade to prettier 3	2025-10-16 11:51:11 +02:00
Damien Arrachequesne	6877512f57	refactor: upgrade to TypeScript 5	2025-10-16 11:49:12 +02:00
Damien Arrachequesne	cf6816afcf	chore: npm audit fix	2025-10-10 09:29:29 +02:00
Damien Arrachequesne	625fd66d73	chore: dedupe debug dependency	2025-10-10 09:11:54 +02:00
Damien Arrachequesne	f3e1f5ebdf	fix(sio): call adapter.init() when creating each namespace The init() method of the adapter will now be called when creating a namespace with `io.of(<the-namespace>)`. Note: any promise rejection is silently caught, as I don't see how we could properly expose the promise. ```js const io = new Server({ adapter: myAdapter }); // under the hood, this: // - implicitly creates the main namespace (/) // - creates an instance of `myAdapter` for the main namespace // - calls `myAdapter.init()` (with this change) ``` Related: - https://github.com/socketio/socket.io/issues/3662 - https://github.com/socketio/socket.io-postgres-adapter/issues/16	2025-10-09 09:48:07 +02:00
Damien Arrachequesne	e97549259e	ci(browser): use Windows 8 for IE tests	2025-09-30 11:44:50 +02:00
MiaoWoo	1da9cddeab	fix(eio-client): properly handle port option (#5241 ) Passing { port: "443" } would include the port in the URL (":443").	2025-09-30 10:57:43 +02:00
Avi Vahl	6f9b198bc8	chore(deps): ws@8.18.3, debug@4.4.1 (#5335 ) Release notes: - https://github.com/websockets/ws/releases/tag/8.18.3 - https://github.com/debug-js/debug/releases/tag/4.4.1	2025-09-11 07:51:07 +02:00
Damien Arrachequesne	ac3df9a747	chore(release): @socket.io/postgres-emitter@0.1.1	2025-09-05 07:27:48 +02:00
Damien Arrachequesne	21fd54ece6	refactor(postgres-emitter): update compose file	2025-09-05 07:20:29 +02:00
Damien Arrachequesne	96d907b9b5	docs(postgres-emitter): add dark version of the explanation diagram	2025-09-05 07:19:07 +02:00
Damien Arrachequesne	32257b6cb8	fix(postgres-emitter): use parameterized query to send the NOTIFY command Related: - https://github.com/socketio/socket.io-postgres-emitter/issues/1 - https://github.com/socketio/socket.io-postgres-adapter/pull/1	2025-09-05 07:18:36 +02:00
Damien Arrachequesne	c7144920e3	Merge remote-tracking branch 'socket.io-postgres-emitter/main' into monorepo	2025-09-04 09:30:26 +02:00
Damien Arrachequesne	42480e9a7f	chore: prepare migration to monorepo	2025-09-04 09:23:32 +02:00
Lou Klepner	0a8f91047c	docs: fix adapter link (#2 )	2025-09-04 09:22:40 +02:00
Damien Arrachequesne	a66ed68506	docs(protocol): add test with cancelled request Related: `8f1ea3d58f`	2025-09-03 09:02:44 +02:00
Damien Arrachequesne	3be6481d9d	ci: pin Node.js 22 version Related: https://github.com/nodejs/node/issues/59364	2025-08-09 09:31:12 +02:00
Wang Guan	be13cca94c	refactor: improve type annotations and comments (#5364 )	2025-08-09 08:43:34 +02:00
Damien Arrachequesne	e95f6abf93	docs: fix message handler latency in test suites Related: https://github.com/socketio/socket.io-protocol/issues/32	2025-03-28 21:29:20 +01:00
Damien Arrachequesne	72d61dab82	chore(release): engine.io@6.6.4 Diff: https://github.com/socketio/socket.io/compare/engine.io@6.6.3...engine.io@6.6.4	2025-01-28 09:23:04 +01:00
Damien Arrachequesne	5a31aaf917	chore(eio): revert cookie to version ~0.7.2 This reverts commit `7427109658`. The new version of the `cookie` package contains code with optional chaining (`?.`), which is not supported by older Node.js versions (< 14). The types for cookie are now bundled, so that there is no conflict with the types coming from `cookie@1`: > error TS2724: '"cookie"' has no exported member named 'CookieSerializeOptions'. Did you mean 'SerializeOptions'? > > import type { CookieSerializeOptions } from "cookie"; > ~~~~~~~~~~~~~~~~~~~~~~ Related: https://github.com/socketio/socket.io/issues/5283	2025-01-28 09:13:39 +01:00
Damien Arrachequesne	56a53bceb9	ci: add Node.js 20 in the test matrix	2023-07-09 10:03:47 +02:00
Damien Arrachequesne	683720a67d	test: fix flaky test	2023-07-09 10:03:46 +02:00
Damien Arrachequesne	a529eb08d6	chore: bump dev dependencies	2023-07-09 10:03:32 +02:00
Damien Arrachequesne	cddb78e5fa	chore(release): 0.2.2 Diff: https://github.com/socketio/socket.io-cluster-adapter/compare/0.2.1...0.2.2	2023-03-24 17:32:35 +01:00
Damien Arrachequesne	15fd56e78d	chore: add socket.io-parser to peerDependencies This should (at least in theory) fix sync issues for the `socket.io-adapter` package, which is imported by both the `socket.io` and `@socket.io/cluster-adapter` packages: - `socket.io@4.5.0` should resolve `socket.io-adapter@~2.4.0` - `socket.io@4.6.0` should resolve `socket.io-adapter@~2.5.0`	2023-03-24 17:28:57 +01:00
Damien Arrachequesne	e86ef45f87	ci: upgrade to actions/checkout@3 and actions/setup-node@3 Reference: https://github.blog/changelog/2022-09-22-github-actions-all-actions-will-begin-running-on-node16-instead-of-node12/	2023-03-24 17:16:25 +01:00
Damien Arrachequesne	fe840e2eb3	chore(release): 0.2.1 Diff: https://github.com/socketio/socket.io-cluster-adapter/compare/0.2.0...0.2.1	2022-10-13 09:23:36 +02:00
Damien Arrachequesne	a5a1c29082	chore: update dev dependencies	2022-10-13 09:17:46 +02:00
Damien Arrachequesne	66b4079953	ci: add Node.js 18 in the test matrix Reference: https://github.com/nodejs/Release	2022-10-13 09:15:34 +02:00
Rolando Andrade	be0a0e3217	fix: properly handle ERR_IPC_CHANNEL_CLOSED errors (#6 ) Related: https://github.com/socketio/socket.io-cluster-adapter/issues/5	2022-10-13 09:11:37 +02:00
Damien Arrachequesne	43f9ee8d23	chore(release): 0.2.0 Diff: https://github.com/socketio/socket.io-cluster-adapter/compare/0.1.0...0.2.0	2022-04-28 16:16:13 +02:00
Damien Arrachequesne	055b7840d8	feat: broadcast and expect multiple acks 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 with multiple Socket.IO servers. Related: https://github.com/socketio/socket.io/issues/4163	2022-04-28 16:11:12 +02:00
Damien Arrachequesne	6397c1bdfd	chore(release): 0.1.0	2021-06-22 07:06:15 +02:00
Damien Arrachequesne	ff370cfc46	Initial commit	2021-06-22 07:02:16 +02:00
Damien Arrachequesne	1f8a6c4ecb	docs: add link to related packages	2021-06-14 08:21:28 +02:00
Damien Arrachequesne	eb01ff5803	chore(release): 0.1.0	2021-06-14 08:02:20 +02:00
Damien Arrachequesne	f2e3d162ab	Initial commit	2021-06-14 07:59:12 +02:00