arvidn/libtorrent
Libtorrent
libtorrent is a portable C++ library that implements the complete BitTorrent protocol for peer-to-peer file transfers, supporting distributed hash tables (DHT), magnet links, and protocol extensions. It provides a well-documented C++ interface for building custom BitTorrent clients with full protocol support, handling peer communication, piece management, and swarm coordination.
The library includes a comprehensive set of protocol components, including peer wire protocol encoding, piece-picking scheduling using rarest-first algorithms, session-based connection management for TCP and uTP connections, and asynchronous disk I/O with a dedicated thread pool. It supports metadata extension for magnet links, tracker communication via HTTP and UDP, and Kademlia-based DHT node implementation for decentralized peer discovery. The storage abstraction layer maps torrent pieces to physical file offsets with support for sparse files and preallocation.
Designed for deployment flexibility, libtorrent can run efficiently on resource-constrained devices like routers and NAS boxes, as well as on servers for seeding and distributing large files. It offers configurable memory and concurrency settings to optimize performance across different hardware environments. The library handles torrent metadata parsing, peer-to-peer file distribution, and swarm-based replication without requiring a central server.
Features
- BitTorrent Client Libraries - Exposes a well-documented C++ interface for building custom BitTorrent clients with full protocol support.
- BitTorrent Protocol Cores - A portable C++ library implementing the complete BitTorrent protocol for peer-to-peer file transfers with DHT, magnet links, and extensions support.
- C++ Networking Libraries - A portable C++ library providing low-level networking and protocol handling for peer-to-peer applications.
- Peer-to-Peer File Distribution - Distributes large files across many recipients without a central server, leveraging swarm-based replication and parallel downloads.
- Storage Abstraction Layers - Maps logical torrent pieces to physical file offsets, supporting sparse files, preallocation, and memory-mapped I/O.
- Rarest-First Piece Selectors - Selects which data blocks to request from peers using a rarest-first algorithm to maximise download throughput and swarm health.
- BitTorrent Clients - A BitTorrent implementation designed to run efficiently on resource-constrained devices with configurable memory and concurrency.
- Embedded - Integrates BitTorrent functionality into resource-constrained devices like routers or NAS boxes with minimal memory and CPU footprint.
- Torrent Metadata Management - Reads and writes .torrent files and magnet links to extract or construct metadata for initiating transfers.
- BitTorrent - Transfers data using the BitTorrent protocol with support for popular extensions for servers and embedded devices.
- Peer Connection Managers - Maintains a pool of TCP and uTP connections to peers, handling handshakes, timeouts, and reconnection logic.
- BitTorrent Wire Protocol Encoders - Serialises and deserialises BitTorrent peer messages into compact binary frames for efficient network transmission.
- Distributed Hash Table Discovery - Participates in the Kademlia-based distributed hash table to find peers without relying on centralised trackers.
- HTTP and UDP Tracker Announcers - Sends periodic HTTP or UDP announcements to trackers to discover peers and report download/upload statistics.
- Thread-Pool Disk I/O Engines - A disk I/O subsystem that manages file reads and writes using a dedicated thread pool to avoid blocking the main network loop.
- Peer-to-Peer Transfer Engines - Implements the complete BitTorrent protocol to transfer files between peers efficiently and scalably.
- Embedded BitTorrent Clients - Optimizes CPU and memory usage to operate reliably on embedded devices and desktops.
- Server-Side Torrenting - Runs BitTorrent clients on servers for seeding, downloading, or distributing large files with configurable resource limits.
- Memory and Concurrency Tuners - Adjusts memory and concurrency settings to run efficiently on servers and resource-constrained devices.
- BitTorrent Metadata Extensions - Parses and serves magnet link metadata via the BitTorrent extension protocol, enabling torrents without a separate .torrent file.
- Bittorrent - Feature-complete library for BitTorrent protocol implementation.
