WebSocket server

Learn to set up a server with new WebSocket.Server.

WebSocket server

Creating a WebSocket server: const wss = new WebSocketServer({ port: 8080 }). This starts a server listening on port 8080. Clients connect to ws://host:8080.

The server listens for connection events. wss.on("connection", (ws) => { ... }) fires on each new client. The ws parameter represents the client connection. You catch messages with ws.on("message", cb) and send with ws.send(data). To close the server call wss.close().

The noServer option

Sometimes you want to attach the WebSocket server to your own HTTP server. The { noServer: true } option does this. Instead of its own port, the server listens to the HTTP server's 'upgrade' event.

This pattern is common for running Express and WebSocket on the same port. server.on("upgrade", (req, socket, head) => { wss.handleUpgrade(req, socket, head, (ws) => { ... }); }). This serves both HTTP and WebSocket on a single port; it is easier behind a production proxy.

Exercise Log the type of WebSocketServer

Import the WebSocketServer class from ws. Log typeof WebSocketServer.

Show example solution

const { WebSocketServer } = require("ws");
console.log(typeof WebSocketServer);

Test yourself

Complete the option name

const wss = new WebSocketServer({ ____: 8080 })

Show answer

const wss = new WebSocketServer({ port: 8080 })

What does new WebSocketServer({ port: 8080 }) do?
- Dosya okur
- Starts a server on port 8080
- Connects a database
- Speeds up the network
Show answer

Starts a server on port 8080 — It starts a WebSocket server on the given port.
Match each piece to its role

new WebSocketServer

Creates a server
wss.on("connection")

On client connect
ws.on("message")

On message
ws.send

Sends a message

Next lesson: Connection

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