Real-Time Communication on the Web

HTTP follows a request-response model where the client initiates every interaction. WebSockets upgrade this to a persistent, bidirectional connection where both client and server can send messages at any time. This enables real-time applications — chat, live notifications, collaborative editing, and live dashboards. At Nexis Limited, WebSockets power real-time shipment tracking in Bondorix and live order updates in Digital Menu.

When to Use WebSockets

  • Live notifications: Push updates to users instantly without polling.
  • Chat and messaging: Bidirectional message exchange between users.
  • Live dashboards: Real-time data visualization with streaming updates.
  • Collaborative editing: Multiple users editing the same document simultaneously.
  • Gaming: Low-latency state synchronization between players.

Do NOT use WebSockets for simple request-response interactions, infrequent updates (use polling or SSE), or file uploads (use HTTP).

Architecture Patterns

Pub/Sub with Redis

In a multi-server deployment, WebSocket connections are distributed across servers. When a message needs to reach a user connected to a different server, Redis pub/sub broadcasts the message to all servers, and each server delivers it to locally connected users. This is our standard pattern for horizontally scaled WebSocket services.

Room-Based Communication

Group related connections into rooms. In Bondorix, each shipment has a room — all users viewing that shipment join its room and receive real-time updates about milestones, document changes, and bid activity. This limits message delivery to interested parties rather than broadcasting to all connections.

Authentication and Security

  • Authenticate during the WebSocket handshake — validate JWT tokens or session cookies before upgrading the HTTP connection to WebSocket.
  • Reject unauthenticated connections immediately — do not allow anonymous WebSocket connections to production services.
  • Implement message-level authorization — verify that the authenticated user has permission to perform the requested action on each message.
  • Rate limit messages to prevent abuse — a compromised client should not be able to flood the server with messages.

Reconnection Strategies

Network interruptions are inevitable. Implement robust reconnection:

  • Detect disconnection immediately using ping/pong heartbeat messages.
  • Reconnect with exponential backoff to avoid overwhelming the server during outages.
  • Re-authenticate on reconnection — tokens may have expired.
  • Re-subscribe to rooms and resume state after reconnection.
  • Buffer messages during disconnection and send them after reconnection.

Scaling WebSockets

  • Each WebSocket connection consumes server memory. Monitor connection counts and plan capacity accordingly.
  • Use sticky sessions or a Redis-based pub/sub layer for multi-server deployments.
  • Consider Socket.IO for its built-in room management, reconnection, and fallback to polling.
  • For very high-scale requirements, consider dedicated WebSocket servers separate from your HTTP API servers.

Alternatives to WebSockets

  • Server-Sent Events (SSE): One-way server-to-client streaming over HTTP. Simpler than WebSockets, supports automatic reconnection, and works with HTTP/2. Use SSE when you only need server-to-client updates (notifications, live feeds).
  • Long Polling: Client makes an HTTP request that the server holds open until new data is available. Simpler to implement but less efficient than WebSockets or SSE.

Conclusion

WebSockets enable genuine real-time communication on the web. Implement them with proper authentication, reconnection handling, and horizontal scaling. For simpler use cases (one-way updates), consider SSE as a lighter alternative. The right choice depends on your communication pattern and scale requirements.

Building a real-time application? Our team has production experience with WebSocket architectures.