This skill should be used when the user asks about "WebSocket in Bun", "real-time communication", "Bun.serve websocket", "ws server", "socket connections", "pub/sub", "broadcasting messages", "WebSocket upgrade", or building real-time applications with Bun.
Bun has built-in WebSocket support integrated with Bun.serve().
const server = Bun.serve({
fetch(req, server) {
// Upgrade to WebSocket
if (server.upgrade(req)) {
return; // Upgraded successfully
}
return new Response("Not a WebSocket request", { status: 400 });
},
websocket: {
open(ws) {
console.log("Client connected");
},
message(ws, message) {
console.log("Received:", message);
ws.send(`Echo: ${message}`);
},
close(ws) {
console.log("Client disconnected");
},
},
});
console.log(`WebSocket server running on ws://localhost:${server.port}`);
Bun.serve({
fetch(req, server) {
server.upgrade(req);
},
websocket: {
// Client connected
open(ws) {
console.log("New connection");
},
// Message received
message(ws, message) {
// message is string | Buffer
if (typeof message === "string") {
console.log("Text:", message);
} else {
console.log("Binary:", message);
}
},
// Connection closed
close(ws, code, reason) {
console.log(`Closed: ${code} - ${reason}`);
},
// Drain event (buffer flushed)
drain(ws) {
console.log("Buffer drained");
},
// Ping received
ping(ws, data) {
// Pong sent automatically
},
// Pong received
pong(ws, data) {
console.log("Pong received");
},
},
});