chore: working on chapter 13

Author: lmammino

13-messaging-and-integration-patterns/01-pubsub-basic-chat/README.md

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+# 01-pubsub-basic-chat
+
+This sample demonstrates the Pub/Sub pattern by implementing a basic chat
+application using WebSockets.
+
+## Dependencies
+
+This example requires you to install some third-party dependencies from npm.
+
+If you have `pnpm` installed, you can do that with:
+
+```bash
+pnpm install
+```
+
+Alternatively, if you prefer to use another package manager, make sure to delete
+the `pnpm-lock.yaml` file before using it.
+
+If you want to use `npm`, you can run:
+
+```bash
+npm install
+```
+
+If you want to use `yarn`, you can run:
+
+```bash
+yarn install
+```
+
+## Run
+
+To run the example server:
+
+```bash
+node index.js <port>
+```
+
+For example, to run the server on port 8080:
+
+```bash
+node index.js 8080
+```
+
+Then you can access the chat application by opening your browser and navigating
+to:
+
+```
+http://localhost:8080
+```

13-messaging-and-integration-patterns/01-pubsub-basic-chat/index.js

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+import { createServer } from 'node:http'
+import staticHandler from 'serve-handler' // v6.1.6
+import { WebSocketServer } from 'ws' // v8.18.2
+
+// serve static files
+const server = createServer((req, res) => {
+  return staticHandler(req, res, { public: 'web' })
+})
+
+const wss = new WebSocketServer({ server })
+wss.on('connection', client => {
+  console.log('Client connected')
+  client.on('message', msg => {
+    console.log(`Message: ${msg}`)
+    broadcast(msg)
+  })
+})
+
+function broadcast(msg) {
+  for (const client of wss.clients) {
+    if (client.readyState === WebSocket.OPEN) {
+      client.send(msg)
+    }
+  }
+}
+
+server.listen(process.argv[2] || 8080)

13-messaging-and-integration-patterns/01-pubsub-basic-chat/package.json

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+{
+  "name": "01-pubsub-basic-chat",
+  "version": "1.0.0",
+  "description": "This sample demonstrates the Pub/Sub pattern by implementing a basic chat application using WebSockets.",
+  "type": "module",
+  "scripts": {},
+  "engines": {
+    "node": ">=24"
+  },
+  "engineStrict": true,
+  "keywords": [],
+  "author": "Luciano Mammino and Mario Casciaro",
+  "license": "MIT",
+  "dependencies": {
+    "serve-handler": "^6.1.6",
+    "ws": "^8.18.2"
+  }
+}