Chart KLines

Chart WebSocket API

Real-time kline (candlestick) data streaming via WebSocket.

Connection

ws://back.dmex.app/ws/chart

Message Format

All messages use JSON with the following structure:

{
  "type": "message_type",
  "data": { ... }
}

Client → Server Messages

Subscribe to Kline Stream

Subscribe to real-time candlestick updates for a symbol/interval pair.

{
  "type": "subscribeKlineStream",
  "data": {
    "symbol": "BTCUSDT",
    "interval": "1m"
  }
}

Parameters:

• symbol - Trading pair (e.g., BTCUSDT, ETHUSDT)

• interval - Candle interval (e.g., 1m, 5m, 15m, 1h, 4h, 1d)

Unsubscribe from Kline Stream

{
  "type": "unsubscribeKlineStream",
  "data": {
    "symbol": "BTCUSDT",
    "interval": "1m"
  }
}

Ping

Keep connection alive with application-level ping.

{
  "type": "ping",
  "data": null
}

Server → Client Messages

Subscription Confirmed

Sent after successful subscription.

{
  "type": "subscriptionConfirmed",
  "data": {
    "symbol": "BTCUSDT",
    "interval": "1m"
  }
}

Kline Stream Update

Real-time candle data pushed to subscribed clients.

{
  "type": "klineStreamUpdate",
  "data": {
    "stream": "btcusdt_1m",
    "data": {
      "k": {
        "t": 1704067200000,
        "o": "42000.00",
        "h": "42150.00",
        "l": "41950.00",
        "c": "42100.00",
        "v": "125.5",
        "x": false
      }
    }
  }
}

Candle fields (k):

Field	Description
t	Candle open time (Unix ms)
o	Open price
h	High price
l	Low price
c	Close price
v	Volume
x	Is candle closed

Pong

Response to client ping.

{
  "type": "pong",
  "data": null
}

Example Usage (JavaScript)

const ws = new WebSocket('ws://back.dmex.app/ws/chart');

ws.onopen = () => {
  // Subscribe to BTC 1-minute candles
  ws.send(JSON.stringify({
    type: 'subscribeKlineStream',
    data: { symbol: 'BTCUSDT', interval: '1m' }
  }));
};

ws.onmessage = (event) => {
  const msg = JSON.parse(event.data);
  
  switch (msg.type) {
    case 'subscriptionConfirmed':
      console.log('Subscribed to:', msg.data.symbol, msg.data.interval);
      break;
    case 'klineStreamUpdate':
      const candle = msg.data.data.k;
      console.log('Candle update:', candle);
      break;
    case 'pong':
      console.log('Pong received');
      break;
  }
};

// Keep-alive ping every 30 seconds
setInterval(() => {
  if (ws.readyState === WebSocket.OPEN) {
    ws.send(JSON.stringify({ type: 'ping', data: null }));
  }
}, 30000);

Connection Management

• Ping/Pong: Server sends WebSocket ping frames every 54 seconds

• Read timeout: 60 seconds (reset on pong)

• Connection cleanup: Stale connections removed after 120 seconds of inactivity

• Throttling: Updates are throttled to max 1 broadcast per 300ms per symbol to prevent flooding

Multiple Subscriptions

You can subscribe to multiple symbol/interval pairs on a single connection:

// Subscribe to multiple streams
ws.send(JSON.stringify({ type: 'subscribeKlineStream', data: { symbol: 'BTCUSDT', interval: '1m' } }));
ws.send(JSON.stringify({ type: 'subscribeKlineStream', data: { symbol: 'BTCUSDT', interval: '5m' } }));
ws.send(JSON.stringify({ type: 'subscribeKlineStream', data: { symbol: 'ETHUSDT', interval: '1m' } }));

Notes

• Symbol names are case-insensitive (internally converted to lowercase)

• Subscription keys are formatted as {symbol}_{interval} (e.g., btcusdt_1m)

• The stream field in updates matches this subscription key format