Manual WebSocket Server

Overview

An engineering lab that implements core WebSocket protocol behavior without a WebSocket framework.

Challenge

Understand WebSocket behavior below framework abstractions while handling connection lifecycle and protocol frames correctly.

Responsibilities

• Implemented the HTTP upgrade handshake
• Encoded and decoded WebSocket frames
• Handled masking, extended payloads, fragmentation, ping/pong, and close frames
• Tracked active connections and implemented broadcast

Solution

Built the upgrade handshake, frame codec, control frames, fragmentation handling, connection tracking, and broadcast directly on Node.js TCP sockets.

Architecture

A Node.js TCP server with explicit HTTP upgrade handling, frame parsing and encoding, connection state, heartbeat control frames, and broadcast.

Technical decisions and trade-offs

• Used raw TCP sockets to expose protocol mechanics
• Kept frame parsing explicit for learning and inspection
• Handled control frames separately from fragmented data messages

Technologies

• Node.js
• JavaScript
• TCP
• WebSocket