WebSocket – 20 Basic Consepts

WebSocket is an important technology for real-time applications that you might work on as a C# .NET developer. Below are 20 key concepts related to WebSocket API architecture, each with an explanation and a C# example.

1. Connection Handshake

The WebSocket connection starts with an HTTP handshake to switch the protocol from HTTP to WebSocket.

// Using System.Net.WebSockets;
ClientWebSocket ws = new ClientWebSocket();
await ws.ConnectAsync(new Uri("ws://localhost:8080"), CancellationToken.None);

2. Full Duplex Communication

WebSocket allows two-way communication between the client and server.

// Sending message
await ws.SendAsync(buffer, WebSocketMessageType.Text, true, CancellationToken.None);

// Receiving message
await ws.ReceiveAsync(new ArraySegment<byte>(recvBuffer), CancellationToken.None);

3. Data Framing

WebSocket messages are divided into frames, facilitating real-time data handling.

// Frame processing is usually abstracted by the library

4. Ping/Pong Mechanism

The ping/pong mechanism helps keep the connection alive.

await ws.SendAsync(new ArraySegment<byte>(pingBuffer), WebSocketMessageType.Ping, true, CancellationToken.None);

5. Message Types

WebSocket supports different message types like Text and Binary.

WebSocketMessageType messageType = WebSocketMessageType.Text;

6. Asynchronous Programming

WebSocket API generally supports async operations for non-blocking behavior.

await ws.ReceiveAsync(new ArraySegment<byte>(buffer), CancellationToken.None);

7. Subprotocols

WebSocket supports different subprotocols for custom behaviors.

ws.Options.AddSubProtocol("soap");

8. Data Compression

WebSocket supports data compression to reduce bandwidth usage.

// This is generally handled by the library

9. Connection Close

Properly closing the WebSocket connection is crucial.

await ws.CloseAsync(WebSocketCloseStatus.NormalClosure, "Close", CancellationToken.None);

10. Error Handling

Error handling during WebSocket operations is essential.

try {
  // WebSocket operation
} catch (WebSocketException e) {
  // Handle exception
}

11. Back-Pressure Handling

Handling back-pressure is essential for high-load scenarios.

// Custom logic to throttle data sending

12. Rate Limiting

Setting rate limits can protect against abuse.

// Implement custom rate-limiting logic

13. Authorization

Securing WebSocket endpoints is crucial.

ws.Options.SetRequestHeader("Authorization", "Bearer YOUR_TOKEN");

14. Connection Reuse

Reusing WebSocket connections can improve performance.

// WebSocket connections are generally long-lived

15. Multiplexing

WebSocket does not natively support multiplexing but it can be implemented.

// Custom logic to share a single WebSocket connection

16. Message Queueing

Using message queues can help in distributing tasks.

// Integrate with existing message queues like RabbitMQ

17. Load Balancing

WebSocket connections can be load-balanced.

// Usually handled by a load balancer and not directly in C#

18. Keep Alive Mechanism

Implementing a keep-alive mechanism ensures that the connection remains active.

// Regularly send ping frames

19. Cross-Origin Security

WebSocket also has to deal with same-origin policy issues.

// Usually handled in server settings

20. Connection Monitoring

Monitoring WebSocket connections is crucial for debugging and scaling.

// Use third-party monitoring tools or custom logic

Pros and Cons

Pros:

1. Low Latency: Ideal for real-time applications.
2. Two-way communication: Full duplex communication.
3. Efficient: Reduces overhead compared to HTTP long polling.

Cons:

1. Complexity: Requires a deeper understanding than REST APIs.
2. Limited Browser Support: Older browsers may not support it.
3. No Built-in Features: Things like rate-limiting, multiplexing need to be implemented manually.

This is a comprehensive overview and should give you a strong grasp of the architecture’s key aspects.