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Connection

Establishes a WebSocket connection for real-time data streams.

Connection URL​

wss://derivatives.api.dlt-finance.com/v1/ws

No authentication is required for public channels. Private channels (orders, trades, margin) require authentication — see below.

Client → Server Messages​

All client messages are JSON objects with an op field.

Subscribe — begin receiving data for one or more topics:

{"op": "subscribe", "args": ["orderbook:BTCUSD_PERP", "orderbook:ETHUSD_PERP"]}

Unsubscribe — stop receiving data for a topic:

{"op": "unsubscribe", "args": ["orderbook:BTCUSD_PERP"]}

Authenticate — authenticate the connection for private channels:

{"op": "authenticate", "public_key": "aabbccdd...", "nonce": "1531816217872000000", "signature": "eeff0011..."}

Ping — check connection liveness:

{"op": "ping"}

Server → Client Messages​

Subscribe acknowledgement — sent after each successful subscription:

{"op": "subscribe", "success": true, "args": ["orderbook:BTCUSD_PERP"]}

Authenticate acknowledgement — sent after successful authentication:

{"op": "authenticate", "success": true}

Error — sent when a request cannot be fulfilled:

{
  "op": "error",
  "code": "UNKNOWN_SYMBOL",
  "message": "Unknown symbol: FOOBAR_PERP",
  "args": ["orderbook:FOOBAR_PERP"]
}

Error codes: UNKNOWN_SYMBOL, ALREADY_SUBSCRIBED, NOT_SUBSCRIBED, INVALID_MESSAGE, AUTHENTICATION_REQUIRED, AUTHENTICATION_FAILED.

Pong — response to a client ping:

{"op": "pong"}

Heartbeat — server-initiated every ~10 s when no data has been sent:

{"op": "heartbeat", "timestamp": "2025-06-15T07:30:00Z"}

Behaviour Notes​

  • One connection supports any number of simultaneous topic subscriptions.
  • Subscribing to an already-subscribed topic returns ALREADY_SUBSCRIBED.
  • Unsubscribing from a topic not currently subscribed returns NOT_SUBSCRIBED.
  • Data begins flowing immediately after a successful subscribe acknowledgement.
  • The server closes the connection after 60 s of inactivity (no messages in either direction).

Authentication​

Private channels require authentication before subscribing. Authentication uses the same ed25519 signature scheme as the REST API, with a fixed method and path.

Signature construction:

message = GET/v1/derivatives/ws{nonce}

Send the authenticate message with your public key, nonce, and signature:

{"op": "authenticate", "public_key": "aabbccdd...", "nonce": "1531816217872000000", "signature": "eeff0011..."}

On success the server responds with:

{"op": "authenticate", "success": true}

On failure the server responds with an error:

{"op": "error", "code": "AUTHENTICATION_FAILED", "message": "Invalid signature"}

Subscribing to a private channel without authenticating first returns:

{"op": "error", "code": "AUTHENTICATION_REQUIRED", "message": "Authentication required for channel: orders", "args": ["orders"]}
  • Authentication applies for the lifetime of the connection.
  • Public channels continue to work without authentication.
  • Private channels: orders, trades, margin, liquidations.