[P0] Implement WebSocket Server for Real-Time Blockchain Event Streaming

[BlocksScanIO]

Feature Request: WebSocket Server for Real-Time Event Streaming

Background

Competitor Analysis Reference: QuickNode, Alchemy, Infura

XDC Gateway currently lacks real-time streaming capabilities. Leading providers like QuickNode offer WebSocket connections for subscribing to live blockchain events with low latency.

Requirements

Core Functionality

• WebSocket server supporting eth_subscribe and eth_unsubscribe methods
• Subscription types:
  • newHeads - New block headers
  • logs - Contract event logs with address/topic filtering
  • newPendingTransactions - Pending transaction pool
  • syncing - Node sync status

Technical Specifications

• Protocol: WebSocket (ws/wss) on port 8546
• Frame Size: Support up to 10MB for large log batches
• Connection Limit: 100 concurrent connections per IP (configurable)
• Heartbeat: Ping/pong every 30 seconds
• Reconnection: Client-side exponential backoff support

Performance Targets

• Latency: <50ms from block import to WebSocket delivery
• Throughput: 1000+ concurrent subscriptions
• Message delivery: At-least-once semantics

Implementation Plan

Phase 1: Core Server (Week 1-2)

// Proposed architecture
package websocket

type Server struct {
    upgrader    websocket.Upgrader
    subscriptions map[string]*Subscription
    blockFeed   chan *types.Block
    eventBus    *EventBus
}

type Subscription struct {
    ID        string
    Type      SubscriptionType
    Filters   FilterCriteria
    Client    *ClientConn
    CreatedAt time.Time
}

Phase 2: Integration (Week 3)

• Hook into XDC node block import pipeline
• Subscribe to internal event feeds
• Implement filtering logic

Phase 3: Testing & Deployment (Week 4)

• Load testing with 10k concurrent connections
• Reorg handling verification
• Documentation and SDK updates

API Specification

// Subscribe request
{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "eth_subscribe",
  "params": ["logs", {"address": "0x...", "topics": ["0x..."]}]
}

// Response
{
  "jsonrpc": "2.0",
  "id": 1,
  "result": "0x9ce59a13059e417087c02d32e8f8f9f8"
}

Acceptance Criteria

• WebSocket endpoint accessible at wss://gateway.xdc.network/ws
• All subscription types functional
• Filter criteria working for logs
• Load test: 1000 concurrent connections, 1 hour stability
• Documentation published

Competitor Comparison

Feature	QuickNode	Alchemy	XDC Gateway (Target)
WebSocket	✅	✅	🔄 In Progress
Subscription Types	4	4	4
Latency	<50ms	<100ms	<50ms
Concurrent	10k+	10k+	1000+

References

• QuickNode WebSocket Guide
• Alchemy WebSocket Docs
• Ethereum JSON-RPC WS Spec

Priority: P0 - Critical for DeFi and real-time applications
Estimated Effort: 4 weeks
Labels: enhancement, infrastructure, P0, websocket