Order Book WebSocket

Streams order book snapshots for a futures symbol.

Event name	FETCH_ORDER_BOOK_CS_PRO
Connection	See Connection for handshake and namespace.

Each push is a full snapshot, not a delta. Replace your local book on every event.

Subscribe

Python

import socketio

sio = socketio.Client()

BASE_URL = "wss://ws.coinswitch.co/"
NAMESPACE = "/exchange_2"
pair = "BTCUSDT"

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_ORDER_BOOK_CS_PRO",
    {"event": "subscribe", "pair": pair},
    namespace=NAMESPACE,
)

@sio.on("FETCH_ORDER_BOOK_CS_PRO", namespace=NAMESPACE)
def on_book(data):
    print("Order book:", data)

sio.wait()

Java

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

String exchange = "exchange_2";
String coinPair = "BTCUSDT";

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_ORDER_BOOK_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_ORDER_BOOK_CS_PRO", map[string]any{
        "event": "subscribe",
        "pair":  "BTCUSDT",
    })
})

sock.On("FETCH_ORDER_BOOK_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_ORDER_BOOK_CS_PRO', { event: 'subscribe', pair: 'BTCUSDT' });
});

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

Update payload

{
  "data": {
    "timestamp": 1732685131699,
    "asks": [
      ["3388.92", "0.10"],
      ["3388.94", "0.01"]
    ],
    "bids": [
      ["3425.71", "2.16"],
      ["3425.69", "0.01"]
    ],
    "symbol": "ETHUSDT"
  }
}

Field	Type	Description
symbol	string	Symbol echoed back.
timestamp	integer	Snapshot time (Unix ms).
bids	array	Sorted descending. Each entry [price, quantity] (both strings).
asks	array	Sorted ascending. Each entry [price, quantity] (both strings).