WebSocket Reference

# Client Upgrade Request GET /chat HTTP/1.1 Host: server.example.com Upgrade: websocket Connection: Upgrade Sec-WebSocket-Key: dGhlIHNhbXBsZSBub25jZQ== Sec-WebSocket-Version: 13 # Server Response (101 Switching Protocols) HTTP/1.1 101 Switching Protocols Upgrade: websocket Connection: Upgrade Sec-WebSocket-Accept: s3pPLMBiTxaQ9kYGzzhZRbK+xOo=

const ws = new WebSocket('wss://example.com/socket'); // Connection opened ws.addEventListener('open', (event) => { ws.send(JSON.stringify({ type: 'subscribe', channel: 'news' })); }); // Listen for messages ws.addEventListener('message', (event) => { const data = JSON.parse(event.data); console.log('Message:', data); }); // Handle errors ws.addEventListener('error', (event) => { console.error('WebSocket error:', event); }); // Connection closed ws.addEventListener('close', (event) => { console.log(`Closed: code=${event.code}, reason=${event.reason}`); }); // Send binary data ws.send(new Uint8Array([1, 2, 3]).buffer); // Close connection ws.close(1000, 'Normal closure');

// Client-side heartbeat function createWebSocket(url) { const ws = new WebSocket(url); let pingInterval; ws.addEventListener('open', () => { pingInterval = setInterval(() => { if (ws.readyState === WebSocket.OPEN) { ws.send(JSON.stringify({ type: 'ping' })); } }, 30000); // ping every 30s }); ws.addEventListener('message', (event) => { const msg = JSON.parse(event.data); if (msg.type === 'pong') return; // ignore pongs // handle real messages }); ws.addEventListener('close', () => { clearInterval(pingInterval); setTimeout(() => createWebSocket(url), 3000); // reconnect }); return ws; }

var upgrader = websocket.Upgrader{ ReadBufferSize: 1024, WriteBufferSize: 1024, CheckOrigin: func(r *http.Request) bool { return true // relax for dev; validate origin in prod }, } func wsHandler(w http.ResponseWriter, r *http.Request) { conn, err := upgrader.Upgrade(w, r, nil) if err != nil { return } defer conn.Close() for { messageType, p, err := conn.ReadMessage() if err != nil { break } if err := conn.WriteMessage(messageType, p); err != nil { break } } }