BitMEX WebSocket and REST API Integration in Delphi

BitMEX is a leading cryptocurrency derivatives exchange specializing in leveraged trading of futures and perpetual contracts. The TsgcWSAPI_Bitmex component provides Delphi developers with both WebSocket and REST API access, enabling real-time market data streaming, order execution, position management, and comprehensive account operations from a single component.

Overview

Unlike many exchange components that only support WebSocket, the TsgcWSAPI_Bitmex component offers a dual-interface approach. The WebSocket API provides real-time streaming of trades, order book updates, quotes, and account data through topic-based subscriptions. The REST API (accessed via the REST_API property) provides synchronous request-response methods for placing orders, managing positions, and querying market data. This combination is ideal for building complete trading applications that need both live data feeds and precise order execution.

Getting Started

Create a TsgcWebSocketClient and a TsgcWSAPI_Bitmex component, link them, and configure your credentials. The WebSocket connection is activated through the client, while the REST API is accessed through the REST_API property.

oClient := TsgcWebSocketClient.Create(nil);
oBitmex := TsgcWSAPI_Bitmex.Create(nil);
oBitmex.Client := oClient;
oBitmex.Bitmex.ApiKey := 'your_api_key';
oBitmex.Bitmex.ApiSecret := 'your_api_secret';
oClient.Active := True;

WebSocket API

The BitMEX WebSocket API uses a topic-based subscription model. You subscribe to a topic (optionally filtered by instrument) and receive a continuous stream of updates. The component provides three core WebSocket methods.

Available Topics

Topics define the type of data you receive. You can subscribe to multiple topics simultaneously. The subscription format is topic:symbol where the symbol filter is optional.

WebSocket Subscription Examples

// Subscribe to XBTUSD trades
oBitmex.Subscribe('trade:XBTUSD');

// Subscribe to the Level 2 order book
oBitmex.Subscribe('orderBookL2:XBTUSD');

// Subscribe to best bid/ask quotes
oBitmex.Subscribe('quote:XBTUSD');

// Authenticate for private topics
oBitmex.Authenticate;

// Subscribe to your order updates (requires auth)
oBitmex.Subscribe('order');

// Subscribe to your position updates (requires auth)
oBitmex.Subscribe('position');

// Unsubscribe from trades
oBitmex.Unsubscribe('trade:XBTUSD');

REST API: Market Data

The REST API is accessed through the REST_API property of the component. Market data methods return JSON strings that you can parse in your application. These are synchronous calls that return immediately with the requested data.

// Get the order book for XBTUSD
ShowMessage(oBitmex.REST_API.GetOrderBook('XBTUSD'));

// Get all active instruments
ShowMessage(oBitmex.REST_API.GetInstrumentsActive);

// Get recent trades
ShowMessage(oBitmex.REST_API.GetTrades('XBTUSD'));

// Get recent quotes
ShowMessage(oBitmex.REST_API.GetQuotes('XBTUSD'));

REST API: Trading

Trading methods allow you to place, amend, and cancel orders. The REST API supports multiple order types including market, limit, stop, and stop-limit orders. All trading methods require authentication.

Order Placement Examples

// Place a limit order: Buy 100 contracts of XBTUSD at $30,000
ShowMessage(oBitmex.REST_API.PlaceLimitOrder(bmsBuy, 'XBTUSD', 100, 30000));

// Place a market order: Sell 50 contracts of XBTUSD
ShowMessage(oBitmex.REST_API.PlaceMarketOrder(bmsSell, 'XBTUSD', 50));

// Place a stop order: triggers when price reaches $28,000
ShowMessage(oBitmex.REST_API.PlaceStopOrder(bmsSell, 'XBTUSD', 100, 28000));

// Place a stop-limit order: triggers at $28,000, limit price $27,500
ShowMessage(oBitmex.REST_API.PlaceStopLimitOrder(bmsSell, 'XBTUSD', 100, 28000, 27500));

// Cancel a specific order
ShowMessage(oBitmex.REST_API.CancelOrder('order-id-here'));

// Cancel all open orders
ShowMessage(oBitmex.REST_API.CancelAllOrders);

REST API: Positions

Position management methods allow you to query, close, and configure your open positions, including leverage and margin settings.

Position Management Examples

// Get current position for XBTUSD
ShowMessage(oBitmex.REST_API.GetPosition('XBTUSD'));

// Set leverage to 10x
ShowMessage(oBitmex.REST_API.SetPositionLeverage('XBTUSD', 10));

// Switch to isolated margin mode
ShowMessage(oBitmex.REST_API.SetPositionIsolate('XBTUSD', True));

// Close the position at market price
ShowMessage(oBitmex.REST_API.ClosePosition('XBTUSD'));

Code Example

The following example demonstrates a complete workflow combining both WebSocket subscriptions and REST API calls: connecting, subscribing to live trades, querying the order book, and placing a limit order.

oClient := TsgcWebSocketClient.Create(nil);
oBitmex := TsgcWSAPI_Bitmex.Create(nil);
oBitmex.Client := oClient;
oBitmex.Bitmex.ApiKey := 'your_api_key';
oBitmex.Bitmex.ApiSecret := 'your_api_secret';
oClient.Active := True;

// Subscribe to trades
oBitmex.Subscribe('trade:XBTUSD');

// REST: Get order book
ShowMessage(oBitmex.REST_API.GetOrderBook('XBTUSD'));

// REST: Place a limit order
ShowMessage(oBitmex.REST_API.PlaceLimitOrder(bmsBuy, 'XBTUSD', 100, 30000));

Configuration and Notes

API Credentials

Generate your API key and secret from the BitMEX account settings. You can create keys with specific permissions (order, withdraw, etc.). For trading bots, create a key with only the permissions you need and avoid enabling withdrawal permissions unless absolutely necessary.

Testnet Support

BitMEX provides a testnet environment at testnet.bitmex.com for development and testing. Configure the component to use the testnet endpoint to test your integration with simulated funds before going live. The Bitmex property group includes settings for selecting between production and testnet environments.

Order Side Enumeration

Trading methods use the bmsBuy and bmsSell enumeration values to specify order direction. These are specific to the BitMEX component.

WebSocket vs REST Usage

Use WebSocket subscriptions for real-time data streaming where low latency is critical (live price displays, order book visualization, execution monitoring). Use the REST API for on-demand operations like placing orders, querying positions, and fetching historical data. The two interfaces complement each other and can be used simultaneously.

Rate Limits

BitMEX enforces rate limits on REST API calls. The limits vary by endpoint but are typically 60 requests per minute for most trading endpoints and 30 requests per minute for order amendment and cancellation. Monitor the rate limit headers in responses to avoid being temporarily blocked. WebSocket subscriptions are not subject to REST rate limits.

Instrument Symbols

BitMEX uses its own instrument symbol format. The perpetual Bitcoin contract is XBTUSD, while futures contracts include an expiry date suffix (e.g., XBTM25). Use GetInstrumentsActive to discover all currently tradeable instruments and their symbols.