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66b7a93 | 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 | /**
* binanceWebSocket.js
* Real-time kline streaming from Binance WebSocket API.
* No API key required.
*/
const BINANCE_WS_BASE = 'wss://stream.binance.com:9443/ws';
const MAX_RECONNECT_DELAY = 30_000; // 30 seconds
export class BinanceStream {
constructor() {
/** @type {WebSocket|null} */
this._ws = null;
/** @type {string|null} */
this._symbol = null;
/** @type {string|null} */
this._interval = null;
/** @type {{ onCandleUpdate?: Function, onTick?: Function }|null} */
this._callbacks = null;
this._reconnectAttempts = 0;
this._reconnectTimer = null;
this._intentionallyClosed = false;
}
/**
* Subscribe to a kline stream.
*
* @param {string} symbol - Lowercase symbol, e.g. 'btcusdt'
* @param {string} interval - Kline interval, e.g. '1m', '5m', '1h'
* @param {{ onCandleUpdate?: (candle: object) => void, onTick?: (price: number) => void }} callbacks
*/
subscribe(symbol, interval, callbacks) {
// Clean up any existing connection first
this.unsubscribe();
this._symbol = symbol.toLowerCase();
this._interval = interval;
this._callbacks = callbacks;
this._intentionallyClosed = false;
this._reconnectAttempts = 0;
this._connect();
}
/** Disconnect from the current stream. */
unsubscribe() {
this._intentionallyClosed = true;
clearTimeout(this._reconnectTimer);
this._reconnectTimer = null;
if (this._ws) {
this._ws.onopen = null;
this._ws.onmessage = null;
this._ws.onerror = null;
this._ws.onclose = null;
this._ws.close();
this._ws = null;
}
this._symbol = null;
this._interval = null;
this._callbacks = null;
}
/* ------------------------------------------------------------------ */
/* Internal */
/* ------------------------------------------------------------------ */
_connect() {
const streamName = `${this._symbol}@kline_${this._interval}`;
const url = `${BINANCE_WS_BASE}/${streamName}`;
console.log(`[BinanceStream] Connecting to ${url}`);
this._ws = new WebSocket(url);
this._ws.onopen = () => {
console.log(`[BinanceStream] Connected – ${streamName}`);
this._reconnectAttempts = 0;
};
this._ws.onmessage = (event) => {
try {
this._handleMessage(JSON.parse(event.data));
} catch (err) {
console.error('[BinanceStream] Error handling message:', err);
}
};
this._ws.onerror = (err) => {
console.error('[BinanceStream] WebSocket error:', err);
};
this._ws.onclose = (event) => {
console.warn(`[BinanceStream] Connection closed (code=${event.code})`);
if (!this._intentionallyClosed) {
this._reconnect();
}
};
}
/**
* Parse a Binance kline WebSocket event.
*
* Binance event shape:
* {
* e: 'kline',
* k: { t, o, h, l, c, v, x, ... }
* }
*/
_handleMessage(msg) {
if (msg.e !== 'kline' || !msg.k) return;
const k = msg.k;
const candle = {
time: Math.floor(k.t / 1000), // ms → seconds
open: parseFloat(k.o),
high: parseFloat(k.h),
low: parseFloat(k.l),
close: parseFloat(k.c),
volume: parseFloat(k.v),
isClosed: k.x,
};
// Always emit the latest close as a tick
if (this._callbacks?.onTick) {
this._callbacks.onTick(candle.close);
}
if (this._callbacks?.onCandleUpdate) {
this._callbacks.onCandleUpdate(candle);
}
}
/** Reconnect with exponential backoff: 1 s → 2 s → 4 s → … → 30 s max. */
_reconnect() {
const delay = Math.min(
1000 * 2 ** this._reconnectAttempts,
MAX_RECONNECT_DELAY,
);
this._reconnectAttempts += 1;
console.log(`[BinanceStream] Reconnecting in ${delay}ms (attempt ${this._reconnectAttempts})`);
this._reconnectTimer = setTimeout(() => {
if (!this._intentionallyClosed) {
this._connect();
}
}, delay);
}
}
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