Realtime Streaming

You can stream realtime market data via WebSocket if you have subscribed to the enterprise package.

The v2 WebSocket streams realtime market data by exchange: traded prices and bid/ask
quotes, for single instruments or a whole exchange with one subscription.

1. Connect

wscat -c "wss://ws.bavest.co/v2" -H "x-api-key: <API KEY>"

Your API key is validated during the handshake. An invalid or missing key rejects the
connection before it opens.

2. Topics

Everything you can subscribe to is a topic:

<channel>.<MIC>.<ISIN>      e.g.  trades.XMUN.DE0007164600
<channel>.<MIC>.*           e.g.  quotes.XMUN.*     (every instrument on the exchange)

Subscribing to an exchange that is not enabled returns an error frame per topic, e.g.
exchange XETR is not enabled.

3. Actions

{"action": "subscribe",   "topics": ["trades.XMUN.DE0007164600", "quotes.XMUN.*"]}
{"action": "unsubscribe", "topics": ["quotes.XMUN.*"]}
{"action": "ping"}

The server acknowledges with {"ev":"subscribed", ...} / {"ev":"unsubscribed", ...} /
{"ev":"pong"}. Invalid topics in a subscribe request are rejected individually with an
error frame; the valid ones still subscribe.

4. Messages

Every server frame carries an ev field. Data frames may arrive batched as a JSON
array (one WebSocket message containing many ticks); control frames (acks, pong,
errors, snapshots) are single objects. Your client must handle both shapes.

Trade (ev: "T", channel trades)

Every trade is delivered; trades are never dropped or merged.

{"ev": "T", "topic": "trades.XMUN.DE0007164600", "x": "XMUN",
 "isin": "DE0007164600", "p": 123.45, "v": 100, "c": "EUR", "t": 1764236768617}

Quote (ev: "Q", channel quotes)

Bid/ask updates, conflated to roughly one message per instrument per second under load
(you always receive the newest state; superseded intermediate quotes are dropped).

{"ev": "Q", "topic": "quotes.XMUN.DE0007164600", "x": "XMUN",
 "isin": "DE0007164600", "bp": 123.40, "bs": 200, "ap": 123.45, "as": 100,
 "c": "EUR", "t": 1764236768617}

Snapshot

Immediately after subscribing to an exact-ISIN topic you receive the last known value
with "snap": true, so you can render current state before the first live tick arrives.

Errors

{"ev": "error", "code": "exchange_not_enabled", "topic": "quotes.XETR.DE0007164600",
 "message": "exchange XETR is not enabled"}

5. Connection lifecycle, heartbeats and reconnects

• Keep-alive: the connection closes after 10 minutes of inactivity. Send
  {"action":"ping"} every 30 to 60 seconds; the server replies {"ev":"pong"}.
• Maximum session length: 2 hours (platform limit). Your client must expect the
  socket to close and reconnect.
• Reconnect best practice: reconnect with exponential backoff and jitter (start at
  1s, double up to a 30s cap, add random jitter). After reconnecting, resubscribe to your
  topics; the snapshots you receive bring you back to current state. Do not reconnect in
  a tight loop: connections are capped per API key, and a reconnect storm will be
  rejected at the handshake.
• Subscription changes become effective within a few seconds. The subscribe snapshot
  reflects current state immediately.

6. Limits

7. Quickstart (Python)

import asyncio, json, random
import websockets

URL = "wss://ws.bavest.co/v2"
TOPICS = ["trades.XMUN.*", "quotes.XMUN.DE0007164600"]

async def stream():
    backoff = 1
    while True:
        try:
            async with websockets.connect(
                URL, extra_headers={"x-api-key": "<API KEY>"}
            ) as ws:
                backoff = 1  # reset after a successful connect
                await ws.send(json.dumps({"action": "subscribe", "topics": TOPICS}))
                async def keepalive():
                    while True:
                        await asyncio.sleep(30)
                        await ws.send(json.dumps({"action": "ping"}))
                asyncio.create_task(keepalive())
                async for message in ws:
                    frames = json.loads(message)
                    for frame in frames if isinstance(frames, list) else [frames]:
                        if frame.get("ev") == "T":
                            print("trade", frame["isin"], frame["p"])
                        elif frame.get("ev") == "Q":
                            print("quote", frame["isin"], frame["bp"], frame["ap"])
        except Exception:
            await asyncio.sleep(backoff + random.random())
            backoff = min(backoff * 2, 30)

asyncio.run(stream())