Multithreaded FTP Server

A multithreaded FTP client-server application built with C++ using TCP sockets and a custom thread pool. Supports multiple concurrent clients, asynchronous command execution, in-flight task termination, and chunked file transfer with a length-prefixed message protocol.

Features

• Concurrent client support: Server handles multiple clients simultaneously using a thread pool, with each client getting its own ClientHandler
• Custom message protocol: Length-prefixed messages in the format $<serverID>#<clientID>#<length>#<message> enable multiplexing multiple operations over a single connection
• Asynchronous commands: Append & to any command to run it in the background (e.g., get largefile.txt &)
• Task termination: Running tasks can be terminated by ID with the terminate command, cancelling in-progress file transfers cleanly
• Chunked file transfer: Files are transferred in configurable chunks with acknowledgment after each chunk
• Dual-socket architecture: Separate normal and terminate sockets per client for out-of-band task cancellation
• Thread pool: Custom thread pool implementation with graceful shutdown support

Architecture

• myftpserver -- Listens on two ports (normal + terminate). For each connecting client, creates a ClientHandler that runs in the thread pool. Receives protocol-formatted messages, parses them, and dispatches FTP commands to worker threads. Each command gets a unique serverID for tracking.
• myftp -- Connects to both server ports. Provides an interactive myftp> prompt. Uses a TaskHandler with a background receive thread to handle asynchronous server responses. Commands can be run synchronously or asynchronously (with &).

Building

make        # builds both myftpserver and myftp
make clean  # removes binaries and object files

Requires a C++ compiler with C++20 support and pthreads.

Usage

1. Start the server with two port numbers (normal and terminate):

   ./myftpserver 8000 8001

2. In another terminal, connect a client:

   ./myftp 8000 8001

3. Available commands at the myftp> prompt:

   • get <filename> -- Download a file from the server
   • put <filename> -- Upload a file to the server
   • delete <filename> -- Delete a file on the server
   • ls -- List files in the server's current directory
   • cd <directory> -- Change the server's working directory
   • mkdir <directory> -- Create a directory on the server
   • pwd -- Print the server's working directory
   • terminate <task_id> -- Cancel a running task by its ID
   • quit -- Disconnect from the server

4. Append & to run a command asynchronously:

   myftp> get largefile.txt &
   myftp> put another.txt &
   

Configuration

The server IP is defined as a preprocessor macro at the top of each source file. Change SERVER_IP before compiling to match your network setup:

#define SERVER_IP "127.0.0.1"