redis-clone

A minimal Redis-like server and client implementation in C/C++.

This project simulates basic Redis functionality using custom socket programming and a simple key-value store, on a single thread with polling, similar to Redis (redis uses epoll). It implements a length-prefixed protocol over TCP, supports concurrent clients using an event-driven polling model, and processes simple commands like SET and GET.

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🛠️ Features

• TCP Server/Client with socket(), bind(), listen(), and connect()
• Non-blocking I/O with poll() for scalable connection handling
• Length-prefixed protocol for structured communication
• Basic Redis-like commands: SET <key> <value>, GET <key>
• In-memory key-value store using std::unordered_map
• Minimal command parsing with error handling
• Graceful shutdown on Ctrl+C (via signal handling)
• Clean CLI interface with custom prompt

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📚 Command Parsing

Reads a single length-prefixed message from a client over TCP.

The protocol format:

+------+--------+------+--------+--------
| len  | msg1   | len  | msg2   | ...
+------+--------+------+--------+--------

Each message consists of:

• A 4-byte little-endian unsigned integer indicating the length of the message body
• A variable-length message body of that length
• This function first reads exactly 4 bytes to determine the length of the incoming message, then reads exactly that many bytes to get the full message body.
• If the client disconnects, or an error occurs during reading, an error is returned.

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⚙️ Architecture

Client (RedisClient)
    -> Connects to server
    -> Sends user commands as length-prefixed messages
    -> Receives and prints server response

Server (RedisServer)
    -> Accepts multiple client connections
    -> Uses poll() to handle many clients in one thread
    -> Parses incoming commands and dispatches handlers
    -> Replies with appropriate result (e.g., OK, value, error)

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🚀 How to run

Prerequisites

• GCC/Clang
• CMake
• Linux environment (or WSL)

Steps

1. cmake -B build
2. cd build
3. make
4. Running
   • Server: ./redis-server
   • Client: ./redis-cli

Note that redis-server must be ran in another terminal prior to running redis-cli.