Aster API WebSocket

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

Limits: 24h; ping 5 min → pong within 15 min; 10 msg/s; max 200 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. id = unsigned int.

Stream names (market)

Stream	Description
`<symbol>@aggTrade`	Aggregate trades (100ms)
`<symbol>@depth`	Diff. book depth (250/500/100ms: `@depth@500ms`, `@depth@100ms`)
`<symbol>@depth5`, `@depth10`, `@depth20`	Partial book depth
`<symbol>@kline_<interval>`	Kline (e.g. 1m, 1h); interval as in REST
`<symbol>@markPrice`, `<symbol>@markPrice@1s`	Mark price (3s or 1s)
`!markPrice@arr`, `!markPrice@arr@1s`	All symbols mark price
`<symbol>@miniTicker`	24h mini ticker (500ms)
`!miniTicker@arr`	All mini tickers (1000ms)
`<symbol>@ticker`	24h ticker (500ms)
`!ticker@arr`	All tickers (1000ms)
`<symbol>@bookTicker`	Best bid/ask (real-time)
`!bookTicker`	All book tickers
`<symbol>@forceOrder`	Liquidation snapshot (1000ms)
`!forceOrder@arr`	All liquidations

User data stream

Start: POST /fapi/v3/listenKey (signed) → { "listenKey": "..." }. If account already has active listenKey, same key returned and validity extended 60 min.
Connect: wss://fstream.asterdex.com/ws/<listenKey>.
Keepalive: PUT /fapi/v3/listenKey (signed) at least every <60 min (e.g. every 30 min).
Close: DELETE /fapi/v3/listenKey (signed).

User data events are not guaranteed in order during heavy load; order updates by event time E.

Events: ACCOUNT_UPDATE (balance/position), ORDER_TRADE_UPDATE, ACCOUNT_CONFIG_UPDATE (leverage, multi-asset, position mode), MARGIN_CALL, listenKeyExpired.

Order book sync (depth stream)

Connect to btcusdt@depth (or combined).
Buffer incoming events.
Get snapshot: GET /fapi/v3/depth?symbol=BTCUSDT&limit=1000.
Drop events with u < snapshot lastUpdateId.
First valid event: U ≤ lastUpdateId and u ≥ lastUpdateId.
Then each event’s pu must equal previous event’s u; else re-sync from step 3.
Quantity in events is absolute; quantity 0 means remove that price level.

Payload shapes: reference.md.