Open-source alternatives to Asio

libuv is a cross-platform asynchronous I/O library that provides an abstraction layer for event-driven networking, filesystem operations, and system signals. It utilizes a non-blocking event loop to coordinate asynchronous tasks and I/O events across different operating systems. The project features a unified interface for managing TCP, UDP, and DNS resolution, alongside an inter-process communication layer for sharing sockets via named pipes and Unix domain sockets. To prevent blocking the main execution loop, it includes a multi-platform thread pool for offloading computationally expensive

Beast is a C++ library for implementing low-level HTTP and WebSocket clients and servers. It functions as an asynchronous networking framework designed to compose non-blocking I/O operations and layered stream stacks for managing concurrent network traffic, specifically utilizing the Boost.Asio asynchronous model. The library provides a comprehensive implementation of the HTTP/1.1 and WebSocket protocols. For HTTP, it includes primitives for parsing and serializing messages with support for chunked transfer encoding, incremental body reading, and request pipelining. Its WebSocket implementati

This project is a technical study and analysis guide focused on the internal architecture of Node.js. It provides an in-depth examination of the runtime, focusing on how the engine manages memory handles, executes asynchronous operations, and implements core module logic. The guide specifically analyzes the integration of native C++ classes and functions into JavaScript and documents the behavior of the libuv event loop. It includes detailed references for optimizing performance by identifying V8 compiler bailouts and profiling execution to improve resource efficiency. The material covers a

Muduo is a C++11 event-driven network library and framework designed for building high-concurrency Linux servers. It provides a toolkit for implementing scalable network services and socket communication using non-blocking I/O and asynchronous event processing. The framework implements a multi-threaded TCP server architecture that distributes connection handling across multiple CPU threads to maximize server throughput. This is achieved through a one-loop-per-thread model and a reactor pattern implementation, which dispatch network events from a central demultiplexer to registered handler fun

async-std is a Rust asynchronous runtime and non-blocking I/O library. It serves as an asynchronous standard library, providing a set of alternatives to the core Rust library for managing concurrent tasks, networking, and file system access. The project implements a standard-library-mirrored API, offering asynchronous versions of existing synchronous types to maintain a familiar interface. This approach allows for asynchronous Rust development using an interface that reflects the ergonomics of the language's standard library. The runtime includes a task executor for scheduling and executing

Boost is a collection of portable, high-performance source libraries that extend the C++ standard library. It provides a wide range of reusable components, data structures, and algorithms designed to add capabilities to the base language across different platforms. The project is distinguished by its extensive focus on compile-time template metaprogramming and generic programming. It implements advanced architectural patterns such as policy-based design, concept-based type validation, and the use of SFINAE for conditional template resolution to minimize runtime overhead. The library covers a

Trio is an asynchronous I/O runtime and concurrency library for Python. It provides a system for executing non-blocking network and disk operations through a centralized event loop and task scheduler. The library is built on a structured concurrency model, which ensures that asynchronous tasks are bound to a specific lifetime and cannot outlive the scope that started them. It utilizes a nursery-based task manager to track task lifecycles in a parent-child tree, preventing orphaned concurrent operations by requiring child tasks to be joined before their parent scope exits. The framework cover

An asynchronous I/O and reactor event loop library for PHP, this project provides core primitives for coordinating non-blocking operations, managing system resources, and scheduling background tasks. The runtime executes concurrent operations by continuously running tick-based loop iterations that process pending timers, network streams, deferred callbacks, and system signals through efficient system-level polling mechanisms. The library coordinates event-driven execution using asynchronous timers for one-off or periodic tasks, next-tick deferred execution for breaking down workloads, and str

monoio is a high-performance asynchronous runtime and executor for Rust. It implements a thread-per-core concurrency model that pins tasks to specific CPU cores to eliminate synchronization overhead and data migration. The runtime leverages the io_uring interface to perform non-blocking system calls and reduce kernel-user mode memory copying. It utilizes a high-performance I/O driver and zero-copy TCP stream wrapping to manage data transfer via shared-memory buffers. The project provides capabilities for CPU core affinity management, low-latency system programming, and high-performance netwo

CocoaAsyncSocket is a networking library for macOS and iOS that provides core components for managing asynchronous TCP and UDP streams. It implements non-blocking network communication to maintain application responsiveness during data transfers, featuring a delegate-based system for managing connection streams and packet handling. The library includes a secure communication layer that wraps TCP sockets to apply encryption standards, protecting client and server traffic from unauthorized interception. Its capabilities cover non-blocking connection management for both stream-based TCP and pac

Swift NIO is a low-level, event-driven network framework for the Swift language. It serves as an asynchronous network protocol stack and I/O library designed to build high-performance network servers and clients that handle thousands of simultaneous connections. The framework functions as a high-concurrency network engine that dispatches events across multiple CPU cores. It enables the implementation of custom network protocols by processing raw bytes through a sequence of reusable data transformation handlers. The system provides capabilities for non-blocking I/O multiplexing, asynchronous

Twisted is an event-driven networking engine for Python that provides a framework for building asynchronous network applications. At its core, it uses a reactor-based event loop to drive all input and output, dispatching callbacks in a single thread without blocking. The library implements a deferred promise chain for composing asynchronous logic, along with a protocol and factory pattern that separates connection state management from protocol handling, enabling reusable handlers for different network protocols. The framework supports multiple event loops across platforms, including select,

This project is a C++ TCP server framework and educational socket programming guide. It provides a high-performance network library focused on event-driven architecture, implementing a reactor pattern to handle thousands of simultaneous client connections. The framework is distinguished by its multi-threaded event loop, which utilizes a main-sub reactor coordination model to distribute network events across a worker thread pool. It includes an abstraction layer for non-blocking socket I/O and event multiplexing via the epoll system call, decoupling network transport from application business

Amp is a non-blocking concurrency framework for PHP. It provides a core infrastructure for writing asynchronous applications using an event loop to schedule operations, timers, and signals within a single process. The project implements a coroutine library that utilizes fibers to suspend and resume function execution. This allows the system to handle concurrent tasks without blocking the main execution thread, optimizing CPU usage during input and output operations. It further manages pending operation results through a future and promise implementation. The framework covers a broad range of

WinFSP is a framework for implementing custom file systems on Windows. It enables the creation of user-mode file systems that appear as standard disk drives or network shares to the operating system, allowing developers to implement file system logic in user space via a proxy architecture that avoids the need for custom kernel code. A primary differentiator is its FUSE compatibility layer, which maps POSIX-based file system calls to native Windows requests. This allows existing file systems written for the FUSE API to be ported to Windows and Cygwin environments. The project covers a wide ra

This project serves as a comprehensive tutorial and technical resource for developing network applications in the C programming language. It focuses on the practical application of the Berkeley socket interface, guiding users through the implementation of low-level network protocols and the management of data transmission across both connection-oriented and connectionless streams. The material distinguishes itself by covering the full lifecycle of network communication, from initializing system-level protocol stacks and resolving domain names to managing complex connection behaviors. It provi

ReactPHP is an asynchronous runtime and event-driven I/O framework for PHP. It provides an environment for executing concurrent tasks through a central event loop implementation and reactor pattern, allowing applications to handle multiple operations without pausing the main execution thread. The project includes a specialized asynchronous socket library for TCP, UDP, and TLS communication, alongside a non-blocking HTTP server and client for streaming web requests and responses. Its capability surface covers asynchronous control flow via promises and fibers, non-blocking network connectivity

Skynet is a distributed game server framework designed for building scalable online game backends. It utilizes distributed actor-based clusters and real-time network communication to manage high-concurrency session coordination across multiple nodes. The framework includes a cluster management orchestrator for coordinating services via cluster-wide messaging and dynamic configuration updates. It features a multi-protocol network gateway supporting TCP, UDP, and WebSockets, alongside a data encoding layer using BSON and Sproto serialization for efficient information transfer between distribute

The MongoDB Python Driver is a client library and NoSQL database client used to execute CRUD operations and manage data within MongoDB databases using the Python programming language. It serves as a database connectivity library that handles authentication and connection pooling, while also providing a vector search client for managing embedding indexes and retrieving data based on semantic similarity. The driver supports both synchronous and asynchronous database driver models to perform non-blocking I/O operations and stream data from database clusters. It distinguishes itself through speci

Okio is a Java I/O library providing a set of tools for efficient byte-stream processing and file system operations. It functions as a buffered byte stream handler and streaming data transformer, utilizing a cross-platform file system API to manage data movement. The project is distinguished by its use of pooled mutable byte buffers that treat sequences as queues to reduce memory copying and garbage collection churn. It further decouples file operations from the host operating system through an abstraction-based file system, allowing for consistent path manipulation and atomic operations acro

Kore is an event-driven web and WebSocket server framework designed for building high-performance web services and APIs in C or Python. It functions as a secure, concurrent application framework that utilizes non-blocking I/O and isolated worker processes to handle high-concurrency traffic. The project is distinguished by a security-first architecture that features OS-level process sandboxing, privilege separation, and the isolation of private encryption keys into dedicated processes. It enables zero-downtime deployments through dynamic module hot-reloading and provides automated TLS certific

This project is a curated educational guide and instructional resource for the Node.js runtime environment. It serves as a comprehensive introduction to core concepts, including asynchronous programming tutorials, network application primers, and guides on the module system and stream API. The material focuses on the fundamental building blocks of server-side development, specifically how to create reusable code packages and manage project dependencies via a module manifest. It provides detailed instruction on building programs that communicate over HTTP and TCP protocols to exchange data acr

This project is a framework for building concurrent, event-driven applications in Ruby. It provides a core engine that orchestrates non-blocking input and output operations, allowing developers to handle high-volume network traffic and system tasks without the complexity of traditional callback-based programming. By leveraging lightweight fibers, the library enables cooperative multitasking that maintains responsiveness during heavy data processing workloads. The framework distinguishes itself through a structured concurrency model that organizes tasks into parent-child hierarchies. This appr

evpp is a C++ network library and framework designed for building high-performance network services using TCP, UDP, and HTTP protocols. It provides an asynchronous event loop to manage nonblocking I/O operations and concurrent network connections across multiple threads. The framework includes specialized tools for asynchronous DNS resolution and a system for asynchronous task scheduling using a managed thread pool. It also features a nonblocking HTTP server and client with integrated connection pooling. The project covers low-level transport layer connectivity for TCP and UDP, as well as hi

Netpoll is an event-driven network framework and non-blocking I/O library designed to manage concurrent TCP and Unix domain socket connections. It utilizes a non-blocking event loop to monitor file descriptors and trigger callbacks for read and write events, serving as a high-performance socket manager and TCP network poller. The framework optimizes throughput across CPU cores by distributing incoming network connections across multiple pollers. It implements zero-copy networking primitives, using linked buffers and specialized memory management to read and write data while minimizing memory

gnet is a high-performance event-driven networking framework for Go, designed for building scalable TCP, UDP, and Unix socket servers. It functions as a non-blocking socket manager and multi-reactor network engine that handles thousands of simultaneous connections with low memory overhead. The framework distinguishes itself by using a multi-reactor architecture that distributes I/O across multiple event loops pinned to operating system threads to minimize context switching. It employs edge-triggered polling to reduce system call frequency and utilizes elastic ring-buffers to minimize allocati

libhv is a high-performance C/C++ network library and event-driven I/O framework used to build TCP, UDP, SSL, HTTP, WebSocket, and MQTT clients and servers. It provides a non-blocking event loop for managing network sockets, timers, and system signals across multiple threads. The project is distinguished by its integrated support for specialized network roles, including a full HTTP web server with RESTful routing and middleware, an MQTT messaging client for IoT communication, and the ability to implement SOCKS5 and HTTP proxies. It also features a reliable UDP implementation to ensure ordered