Poly-WebSockets

A TypeScript library for real-time Polymarket market data over WebSocket with automatic reconnections and easy subscription management.

Powering Nevua Markets

Installation

npm install @nevuamarkets/poly-websockets

Features

• 📊 Real-time Market Updates: Get book, price_change, tick_size_change and last_trade_price events from Polymarket WebSocket
• 🎯 Derived Price Event: Implements Polymarket's price calculation logic (midpoint vs last trade price based on spread)
• 🔗 Dynamic Subscriptions: Subscribe and unsubscribe to assets without reconnecting
• 🔄 Automatic Reconnection: Handles connection drops with automatic reconnection
• 💪 TypeScript Support: Full TypeScript definitions for all events and handlers
• 🔒 Independent Instances: Each manager instance is fully isolated with its own WebSocket connection

Quick Start

import { WSSubscriptionManager } from '@nevuamarkets/poly-websockets';

const manager = new WSSubscriptionManager({
  onBook: async (events) => {
    console.log('Book events:', events);
  },
  onPriceChange: async (events) => {
    console.log('Price change events:', events);
  },
  onPolymarketPriceUpdate: async (events) => {
    // Derived price following Polymarket's display logic
    console.log('Price updates:', events);
  },
  onError: async (error) => {
    console.error('Error:', error.message);
  }
});

// Subscribe to assets
await manager.addSubscriptions(['asset-id-1', 'asset-id-2']);

// Get monitored assets
console.log('Monitored:', manager.getAssetIds());

// Remove subscriptions
await manager.removeSubscriptions(['asset-id-1']);

// Clear all subscriptions and close connection
await manager.clearState();

API Reference

WSSubscriptionManager

Constructor

new WSSubscriptionManager(handlers: WebSocketHandlers, options?: SubscriptionManagerOptions)

Parameters:

• handlers - Event handlers for WebSocket events
• options - Optional configuration:
  • reconnectAndCleanupIntervalMs?: number - Reconnection check interval (default: 5000ms)
  • pendingFlushIntervalMs?: number - How often to flush pending subscriptions (default: 100ms)

Methods

Method	Description
addSubscriptions(assetIds: string[])	Add assets to monitor
removeSubscriptions(assetIds: string[])	Stop monitoring assets
getAssetIds(): string[]	Get all monitored asset IDs (subscribed + pending)
getStatistics()	Get connection and subscription statistics
clearState()	Clear all subscriptions and close connection

Statistics Object

manager.getStatistics() // Returns:
{
  openWebSockets: number;           // 1 if connected, 0 otherwise
  assetIds: number;                 // Total monitored assets
  pendingSubscribeCount: number;    // Assets waiting to be subscribed
  pendingUnsubscribeCount: number;  // Assets waiting to be unsubscribed
}

WebSocketHandlers

interface WebSocketHandlers {
  // Polymarket WebSocket events
  onBook?: (events: BookEvent[]) => Promise<void>;
  onLastTradePrice?: (events: LastTradePriceEvent[]) => Promise<void>;
  onPriceChange?: (events: PriceChangeEvent[]) => Promise<void>;
  onTickSizeChange?: (events: TickSizeChangeEvent[]) => Promise<void>;
  
  // Derived price update (implements Polymarket's display logic)
  onPolymarketPriceUpdate?: (events: PolymarketPriceUpdateEvent[]) => Promise<void>;
  
  // Connection events
  onWSOpen?: (managerId: string, pendingAssetIds: string[]) => Promise<void>;
  onWSClose?: (managerId: string, code: number, reason: string) => Promise<void>;
  onError?: (error: Error) => Promise<void>;
}

Event Types

Event	Description
BookEvent	Full order book snapshot (docs)
PriceChangeEvent	Order book price level changes (docs)
TickSizeChangeEvent	Tick size changes (docs)
LastTradePriceEvent	Trade executions
PolymarketPriceUpdateEvent	Derived price using Polymarket's display logic

Multiple Independent Connections

Each WSSubscriptionManager instance maintains its own WebSocket connection:

// Two separate connections for different asset groups
const manager1 = new WSSubscriptionManager(handlers1);
const manager2 = new WSSubscriptionManager(handlers2);

await manager1.addSubscriptions(['asset-1', 'asset-2']);
await manager2.addSubscriptions(['asset-3', 'asset-4']);

Examples

See the examples folder for complete working examples.

Testing

npm test

License

AGPL-3.0

Disclaimer

This software is provided "as is", without warranty of any kind. The author(s) are not responsible for any financial losses, trading decisions, bugs, or system failures. Use at your own risk.