WebSockets Course

Lesson 1 • WebSocket Protocol Fundamentals

Defines the WebSocket protocol, its RFC specification, and its role in enabling full-duplex communication. Grounds students in the technical definition before implementation.

Lesson 2 • The WebSocket Handshake Process

Explains the HTTP upgrade mechanism that initiates a WebSocket connection. Students understand how a standard HTTP request transitions to a persistent WebSocket channel.

Lesson 3 • WebSocket versus HTTP Architecture

Contrasts WebSocket and HTTP at the architectural level, covering connection lifecycle differences. Prepares students to choose the right protocol for a given scenario.

Lesson 1 • Managing Connection Lifecycle Events

Covers open, message, error, and close events on both client and server sides. Students learn to handle each lifecycle phase cleanly and predictably.

Lesson 2 • Creating a Basic WebSocket Server

Walks through writing a minimal server that listens for WebSocket connections and echoes messages. Introduces core server-side event handlers used throughout the course.

Lesson 3 • Setting Up the Development Environment

Covers tool selection, runtime installation, and project scaffolding for WebSocket development. Ensures every student starts with a consistent, working environment.

Lesson 4 • Testing the Connection with Developer Tools

Demonstrates how to inspect WebSocket frames in browser developer tools and network panels. Students gain confidence in verifying that their connections behave as expected.

Lesson 1 • Binary Data Transmission

Introduces ArrayBuffer and Blob types for sending binary payloads over WebSockets. Students can transfer images, audio, and other binary content efficiently.

Lesson 2 • WebSocket Frame Structure

Breaks down the WebSocket frame format including opcode, masking, and payload length fields. Provides the low-level knowledge needed to understand protocol behaviour and debugging.

Lesson 3 • Sending and Receiving Text Messages

Covers UTF-8 encoding requirements for text frames and common serialisation patterns. Students can reliably exchange human-readable data between client and server.

Lesson 4 • Working with JSON Payloads

Establishes JSON as the standard structured data format for WebSocket messages. Students design and parse typed message envelopes for real application use.

Lesson 1 • Rooms and Namespaces for Targeted Messaging

Introduces logical grouping of connections into rooms for scoped message delivery. Students implement room join, leave, and targeted broadcast operations.

Lesson 2 • Heartbeat and Ping-Pong Mechanisms

Explains WebSocket ping and pong frames used to detect stale connections. Students implement a server-side heartbeat loop that cleans up dead clients automatically.

Lesson 3 • Broadcasting Messages to All Clients

Implements server-side broadcast so every connected client receives a message simultaneously. Students build the core publish mechanism underlying chat and live-feed applications.

Lesson 4 • Managing Multiple Client Connections

Covers data structures and patterns for tracking all active WebSocket clients on the server. Students implement a connection registry used in every subsequent server feature.

Lesson 1 • Session Expiry and Token Refresh

Handles token expiration during long-lived WebSocket sessions without forcing reconnection. Students implement server-initiated token refresh and graceful session termination.

Lesson 2 • Token-Based Authentication at Handshake

Implements JWT or opaque token validation during the HTTP upgrade request. Students secure the connection entry point before any messages are exchanged.

Lesson 3 • Post-Handshake Authentication Messages

Covers an alternative pattern where the client sends credentials as the first message after connecting. Students implement an auth handshake message flow with timeout enforcement.

Lesson 4 • Authentication Challenges in WebSockets

Highlights why standard cookie and session auth patterns are unreliable for WebSocket upgrades. Motivates token-based approaches covered in subsequent sections.

Lesson 1 • Shared State with Distributed Caches

Uses a distributed cache to store room membership and user presence data accessible by all server instances. Students eliminate per-instance state that breaks at scale.

Lesson 2 • The Horizontal Scaling Problem

Explains why a client connected to server A cannot receive messages broadcast from server B. Frames the need for a shared pub/sub layer as the core scaling solution.

Lesson 3 • Integrating a Message Broker

Connects each WebSocket server instance to a central pub/sub broker for cross-server message delivery. Students implement subscribe and publish operations from the server process.

Lesson 4 • Monitoring and Observability at Scale

Instruments WebSocket servers with metrics, structured logs, and distributed tracing. Students can diagnose performance bottlenecks and connection anomalies in production.

Lesson 1 • Securing Connections with TLS

Enforces encrypted WebSocket connections using the wss:// scheme and proper TLS configuration. Students configure certificates and eliminate plaintext WebSocket exposure.

Lesson 2 • Input Validation and Injection Prevention

Validates and sanitizes every incoming WebSocket message to prevent injection and deserialization attacks. Students apply schema validation as the first processing step.

Lesson 3 • Rate Limiting and Denial-of-Service Protection

Implements per-connection and per-user message rate limits to prevent resource exhaustion. Students configure connection throttling and automatic offender disconnection.

Lesson 4 • Dependency and Library Security

Addresses vulnerabilities introduced through third-party WebSocket libraries and their dependencies. Students establish a process for auditing and updating dependencies safely.

Lesson 1 • Connection Pooling and Resource Management

Manages server resources by limiting concurrent connections and reusing downstream connections. Students prevent resource exhaustion under high connection load.

Lesson 2 • Containerisation and Orchestration

Packages the WebSocket server in a container and deploys it with an orchestrator for automated scaling. Students configure health checks and rolling updates without dropping connections.

Lesson 3 • Optimising Message Throughput

Applies batching, compression, and serialisation optimisations to maximise messages per second. Students reduce per-message overhead without sacrificing reliability.

Lesson 4 • Performance Profiling and Bottleneck Identification

Uses profiling tools to locate CPU, memory, and I/O bottlenecks in WebSocket server code. Students establish a baseline and measure the impact of each optimisation.