Aster Spot API WebSocket (v1)

Base: wss://sstream.asterdex.com. Raw: /ws/<streamName>. Combined: /stream?streams=name1/name2/... → {"stream":"<name>","data":<payload>}. Stream names lowercase (e.g. btcusdt).

Limits: Connection 24h; ping every 5 min → pong within 15 min; 5 msg/s; max 1024 streams.

Market: subscribe / unsubscribe

JSON: Subscribe {"method":"SUBSCRIBE","params":["btcusdt@aggTrade","btcusdt@depth"],"id":1} → {"result":null,"id":1}. Unsubscribe: UNSUBSCRIBE + params. List: LIST_SUBSCRIPTIONS.

Stream names (market)

User data stream (USER_STREAM)

1. Start: POST /api/v1/listenKey → { "listenKey": "..." } (existing key extended 60 min). API key in header.
2. Connect: wss://sstream.asterdex.com/ws/.
3. Keepalive: PUT /api/v1/listenKey with listenKey (e.g. every 30 min).
4. Close: DELETE /api/v1/listenKey with listenKey.

Events: outboundAccountPosition (balance), executionReport (order update).

Order book sync (depth)

1. Subscribe to <symbol>@depth; buffer events.
2. Snapshot: GET /api/v1/depth?symbol=SYMBOL&limit=1000.
3. Discard events with u ≤ lastUpdateId; first valid: U ≤ lastUpdateId+1 and u ≥ lastUpdateId+1.
4. Each event: pu = previous u; else re-sync. Qty absolute; 0 = remove level.

Payload shapes: reference.md.