KLines WebSocket

Streams real-time candle updates for a futures symbol at a chosen interval. Used to render live charts.

Event name	FETCH_CANDLESTICK_CS_PRO
Connection	See Connection.

Pair format — SYMBOL_INTERVAL

The pair field on the subscribe payload is SYMBOL_INTERVAL (with an underscore), where INTERVAL is in minutes. This is different from every other futures WebSocket (which use just SYMBOL).

Pattern	Description
BTCUSDT_5	5-minute BTCUSDT candles
ETHUSDT_15	15-minute ETHUSDT candles
DOGEUSDT_60	1-hour DOGEUSDT candles

Subscribe

Python

import socketio

sio = socketio.Client()

BASE_URL = "wss://ws.coinswitch.co/"
NAMESPACE = "/exchange_2"
pair = "BTCUSDT_5"   # SYMBOL_INTERVAL

sio.connect(
    url=BASE_URL,
    namespaces=[NAMESPACE],
    transports="websocket",
    socketio_path="/pro/realtime-rates-socket/futures/exchange_2",
    wait=True,
    wait_timeout=3600,
)

sio.emit(
    "FETCH_CANDLESTICK_CS_PRO",
    {"event": "subscribe", "pair": pair},
    namespace=NAMESPACE,
)

@sio.on("FETCH_CANDLESTICK_CS_PRO", namespace=NAMESPACE)
def on_kline(data):
    print("Kline:", data)

sio.wait()

Java

import okhttp3.*;
import org.json.JSONObject;

String exchange = "exchange_2";
String coinPair = "BTCUSDT_5";   // SYMBOL_INTERVAL

OkHttpClient client = new OkHttpClient();
Request request = new Request.Builder()
    .url("wss://ws.coinswitch.co/pro/realtime-rates-socket/futures/?EIO=4&transport=websocket")
    .build();

JSONObject subscribe = new JSONObject()
    .put("event", "subscribe")
    .put("pair", coinPair);

String namespaceFrame = "40/" + exchange + ",";
String subscribeFrame = "42/" + exchange + ",[\"FETCH_CANDLESTICK_CS_PRO\"," + subscribe + "]";

WebSocket ws = client.newWebSocket(request, new WebSocketListener() { /* ... */ });
ws.send(namespaceFrame);
ws.send(subscribeFrame);

Go

import (
    "log"
    socketio "github.com/zishang520/socket.io-client-go/v2/client"
)

opts := socketio.DefaultOptions()
opts.SetTransports([]string{"websocket"})
opts.SetPath("/pro/realtime-rates-socket/futures/exchange_2")

sock := socketio.Connect("wss://ws.coinswitch.co/exchange_2", opts)
defer sock.Close()

sock.On("connect", func(args ...any) {
    sock.Emit("FETCH_CANDLESTICK_CS_PRO", map[string]any{
        "event": "subscribe",
        "pair":  "BTCUSDT_5",
    })
})

sock.On("FETCH_CANDLESTICK_CS_PRO", func(args ...any) {
    log.Println("update:", args)
})

select {}

Node.js

// npm install socket.io-client@^4
const { io } = require('socket.io-client');

const sock = io('wss://ws.coinswitch.co/exchange_2', {
  path: '/pro/realtime-rates-socket/futures/exchange_2',
  transports: ['websocket'],
});

sock.on('connect', () => {
  sock.emit('FETCH_CANDLESTICK_CS_PRO', { event: 'subscribe', pair: 'BTCUSDT_5' });
});

sock.on('FETCH_CANDLESTICK_CS_PRO', (data) => {
  console.log('update:', data);
});

Update payload

{
  "o": "104562.7",
  "h": "104588.5",
  "l": "104535",
  "c": "104558.7",
  "v": "43.205",
  "q": "1918381.4344",
  "s": "BTCUSDT",
  "i": "5",
  "x": false,
  "t": 1734343500000,
  "T": 1734343799999,
  "ts": 1734343543430
}

Field	Type	Description
s	string	Symbol.
i	string	Interval in minutes.
o / h / l / c	string	Open / high / low / close.
v	string	Base-asset volume during the candle.
q	string	Quote-asset (USDT) volume during the candle.
t	integer	Candle start time (Unix ms).
T	integer	Candle close time (Unix ms).
ts	integer	Time of the most recent trade in this candle (Unix ms).
x	boolean	true if this candle is closed (final). false while it's still updating.

While a candle is open, x is false and you'll receive multiple updates as new trades print. When the interval boundary passes, you receive a final update with x = true, then the first update for the next candle.