Usage with bundlers

While less common than frontend bundling, it is totally possible to create a bundle for the server.

Webpack 5

Without serving the client files

Installation:

npm install -D webpack webpack-cli socket.io bufferutil utf-8-validate

index.js

const { Server } = require("socket.io");

const io = new Server({
  serveClient: false
});

io.on("connection", socket => {
  console.log(`connect ${socket.id}`);

  socket.on("disconnect", (reason) => {
    console.log(`disconnect ${socket.id} due to ${reason}`);
  });
});

io.listen(3000);

webpack.config.js

const path = require("path");

module.exports = {
  entry: "./index.js",
  target: "node",
  mode: "production",
  output: {
    path: path.resolve(__dirname, "dist"),
    filename: "index.js",
  }
};

Note: bufferutil and utf-8-validate are two optional dependencies from the ws package. You can also set them as "external" with:

const path = require("path");

module.exports = {
  entry: "./index.js",
  target: "node",
  mode: "production",
  output: {
    path: path.resolve(__dirname, "dist"),
    filename: "index.js",
  },
  externals: {
    bufferutil: "bufferutil",
    "utf-8-validate": "utf-8-validate",
  },
};

Documentation: https://webpack.js.org/configuration/externals/

Including serving the client files

In that case, we'll have to use Asset modules and override the sendFile function of the Socket.IO server:

index.js

const { Server } = require("socket.io");

const clientFile = require("./node_modules/socket.io/client-dist/socket.io.min?raw");
const clientMap = require("./node_modules/socket.io/client-dist/socket.io.min.js.map?raw");

Server.sendFile = (filename, req, res) => {
  res.end(filename.endsWith(".map") ? clientMap : clientFile);
};

const io = new Server();

io.on("connection", socket => {
  console.log(`connect ${socket.id}`);

  socket.on("disconnect", (reason) => {
    console.log(`disconnect ${socket.id} due to ${reason}`);
  });
});

io.listen(3000);

webpack.config.js

const path = require("path");

module.exports = {
  entry: "./index.js",
  target: "node",
  mode: "production",
  output: {
    path: path.resolve(__dirname, "dist"),
    filename: "index.js",
  },
  module: {
    rules: [
      {
        resourceQuery: /raw/,
        type: "asset/source",
      },
    ],
  },
};