WebSocket Protocol Cheat Sheet

// Open connection (`ws://` or secure `wss://`)
const socket = new WebSocket("wss://echo.websocket.events");

// Event: Connection established
socket.onopen = (event) => {
  console.log("WebSocket connection established");
  socket.send(JSON.stringify({ type: "ping", time: Date.now() }));
};

// Event: Message received from server
socket.onmessage = (event) => {
  const data = JSON.parse(event.data);
  console.log("Server message received:", data);
};

// Event: Error occurred
socket.onerror = (error) => {
  console.error("WebSocket error:", error);
};

// Event: Connection closed
socket.onclose = (event) => {
  console.log(`Connection closed cleanly: ${event.wasClean}, Code: ${event.code}`);
};

GET /chat HTTP/1.1
Host: server.example.com
Upgrade: websocket
Connection: Upgrade
Sec-WebSocket-Key: dGhlIHNhbXBsZSBub25jZQ==
Sec-WebSocket-Version: 13

HTTP/1.1 101 Switching Protocols
Upgrade: websocket
Connection: Upgrade
Sec-WebSocket-Accept: s3pPLMBiTxaQ9kYGzzhZRbK+xOo=