在建立 WebSocket 伺服器時，通常需要儲存一些識別資訊或與每個已連線用戶端相關的內容。
使用 Bun.serve()，在連線最初升級時，透過在 server.upgrade() 呼叫中傳遞 data 參數來設定這個「上下文資料」。
Bun.serve<{ socketId: number }>({
fetch(req, server) {
const success = server.upgrade(req, {
data: {
socketId: Math.random(),
},
});
if (success) return undefined;
// handle HTTP request normally
// ...
},
websocket: {
// define websocket handlers
async message(ws, message) {
// the contextual dta is available as the `data` property
// on the WebSocket instance
console.log(`Received ${message} from ${ws.data.socketId}}`);
},
},
});
從傳入的請求中讀取 cookie/標頭以識別連線的用戶端是很常見的作法。
type WebSocketData = {
createdAt: number;
token: string;
userId: string;
};
// TypeScript: specify the type of `data`
Bun.serve<WebSocketData>({
async fetch(req, server) {
// use a library to parse cookies
const cookies = parseCookies(req.headers.get("Cookie"));
const token = cookies["X-Token"];
const user = await getUserFromToken(token);
const upgraded = server.upgrade(req, {
data: {
createdAt: Date.now(),
token: cookies["X-Token"],
userId: user.id,
},
});
if (upgraded) return undefined;
},
websocket: {
async message(ws, message) {
// save the message to a database
await saveMessageToDatabase({
message: String(message),
userId: ws.data.userId,
});
},
},
});