Open-source alternatives to UWebSockets

NanoHTTPD is a lightweight, embeddable HTTP server for Java applications. It allows developers to integrate web server capabilities directly into a Java project to handle incoming requests without requiring a standalone installation. The project provides specialized implementations for an HTTPS web server, a WebSocket server for bidirectional real-time communication, and a static file web server. These capabilities enable secure network traffic through SSL certificates and the delivery of local files with automatic MIME type detection. The server includes systems for request routing and hand

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 is a header-only C++ library that provides implementations for HTTP clients, HTTP servers, and a WebSocket framework. It allows for the creation of network services and the consumption of remote APIs without requiring a separate compilation step or external binary linking. The project features backend-agnostic TLS integration for secure HTTPS and WSS communication and employs a thread-pool model to process concurrent requests. It distinguishes itself with a full-duplex WebSocket state-machine and a middleware-based request pipeline that supports regular-expression path routing. The libr

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

libwebsockets is an event-driven networking framework written in C. It provides a suite of tools for implementing HTTP servers and clients, WebSocket bidirectional communication, MQTT client messaging, and TLS-enabled socket encryption. The project distinguishes itself through a non-blocking event-loop architecture capable of scaling to high connection volumes by distributing network sessions across multiple service threads. It uses a protocol-based callback system and a pluggable event loop integration that allows the networking core to synchronize with external system event libraries. The

Highly scalable realtime pub/sub and RPC framework

This project is a cross-platform C library designed for implementing MQTT messaging in applications. It serves as an asynchronous networking toolkit that enables resource-constrained systems and distributed components to exchange telemetry data and control signals with messaging brokers. The library distinguishes itself through a state-machine-based protocol handler that manages connection lifecycles and persistent session states, ensuring reliable message delivery even during intermittent network connectivity. It utilizes a background thread to manage network operations, allowing application

MQTT.js is a JavaScript client library and asynchronous messaging client used to connect to message brokers and exchange data via the MQTT protocol. It provides a broker interface for publishing and subscribing to topics, and includes a command-line interface for interacting with brokers without writing code. The library supports multiple network layers, including TCP, TLS, and WebSockets, and allows for custom WebSocket construction and transport injection to handle specific headers or subprotocols. It implements bandwidth reduction through topic aliasing, which replaces repetitive topic str

Gevent is a Python coroutine concurrency library and asynchronous task manager designed for high-concurrency I/O tasks. It provides a cooperative networking framework for building asynchronous TCP, UDP, and HTTP servers, as well as a WSGI web server implementation for hosting web applications. The project is distinguished by its standard library monkey-patching tool, which replaces blocking synchronous functions with cooperative versions to enable asynchronous behavior in third-party code. This allows for a cooperative multitasking workflow where the system yields execution during I/O waits t

NATS Server is a high-performance, lightweight messaging system designed for cloud-native applications, edge computing, and distributed microservices. It functions as a distributed publish-subscribe broker that routes messages using hierarchical, dot-separated subject strings, enabling decoupled communication between services without requiring centralized broker lookups. The system supports core messaging patterns including asynchronous publish-subscribe, request-reply, and load-balanced queue processing. The platform distinguishes itself through a decentralized architecture that eliminates t

Spin is a WebAssembly serverless framework and development toolchain for building and running portable microservices. It functions as an event-driven orchestrator and runtime that executes WebAssembly components, allowing developers to map HTTP requests, Redis messages, and cron schedules to specific modules. The project distinguishes itself by implementing a Wasm-based AI inference gateway, enabling components to perform model inference and generate text embeddings. It utilizes the WebAssembly Component Model and WASI for language-agnostic composition and portable host interfacing, while emp

Cerbos is an open-source authorization service that provides a centralized, language-agnostic engine for managing access control. It functions as a policy-as-code platform, allowing teams to define, test, and distribute authorization rules using declarative YAML or JSON configurations. By decoupling access logic from application code, it enables consistent permission enforcement across diverse service stacks. The project distinguishes itself through its ability to translate high-level authorization policies into native database query filters. This capability allows applications to enforce sec

Japronto is an asynchronous web framework and Python HTTP server toolkit. It functions as a multi-worker HTTP server and request router, utilizing non-blocking asynchronous handlers to manage high concurrency and throughput. The project implements a master-multiworker forking model to distribute network traffic across multiple CPU cores. It incorporates a fast event loop and a specialized C-extension for high-speed HTTP request parsing, while supporting request pipelining over single TCP connections. The framework covers a broad range of request handling capabilities, including URL pattern r

Fasthttp is a high-performance networking framework for Go, designed to maximize throughput and minimize memory overhead in demanding web applications. It functions as a specialized HTTP server and client library that prioritizes efficient resource management, allowing developers to build scalable services capable of handling massive concurrent traffic with minimal garbage collection pressure. The library distinguishes itself through a focus on zero-allocation processing and low-level optimization. It achieves this by recycling temporary request and response objects through managed pools and

Hyperf is a high-performance PHP coroutine framework designed for building microservices and middleware. It utilizes non-blocking coroutines to handle high concurrency and low-latency request processing, providing a foundation for scalable distributed systems. The framework is distinguished by an aspect-oriented programming based dependency injector that enables pluggable components and meta-programming. It includes a coroutine-optimized object-relational mapper with integrated model caching and an orchestration toolkit for microservice governance, featuring service discovery, circuit breaker

h2o is a high-performance content delivery server and HTTP/3 web server. It functions as a network gateway and reverse proxy that forwards client requests to upstream servers to manage traffic flow and load. The project distinguishes itself as a protocol fuzzing tool, utilizing a testing framework to execute automated stress tests against network protocols to identify memory leaks and crashes. The server provides capabilities for secure web traffic management through encrypted data transmission and high-performance web serving across HTTP/1, HTTP/2, and HTTP/3. It includes tools for server r

Undertow is a Java HTTP web server and non-blocking I/O server implementation. It functions as a Jakarta Servlet container and a WebSocket server, providing the infrastructure to execute standardized servlet components and maintain persistent full-duplex communication channels for real-time data exchange. The project is characterized by an asynchronous architecture that utilizes a non-blocking I/O model to handle large numbers of concurrent connections. It incorporates buffer-pooling mechanisms and zero-copy data transfers to reduce memory allocation and garbage collection pressure. The syst

aiohttp is an asynchronous networking framework for Python that provides both an HTTP client and an HTTP server. It utilizes the asyncio library to handle network requests and server-side routing through a non-blocking event loop. The framework includes a dedicated toolkit for establishing persistent bidirectional communication channels, enabling the implementation of both WebSocket servers and clients for real-time data exchange. It covers a broad range of asynchronous network programming capabilities, including the development of web servers with customizable routing and the ability to sen

Hyper is a low-level networking library designed for building high-performance HTTP clients and servers. It provides a foundational toolkit for creating network services that leverage asynchronous execution and memory-safe data handling, supporting both HTTP/1 and HTTP/2 protocols. The library distinguishes itself through a protocol-agnostic architecture that separates transport logic from HTTP semantics. It utilizes a service-trait abstraction to decouple network logic from the underlying transport, enabling developers to inject custom middleware for request interception and response transfo

Oak is a cross-runtime HTTP middleware framework and web server designed to operate across Deno, Node.js, Bun, and Cloudflare Workers. It provides a unified system for building APIs and web servers using a sequential chain of middleware functions and a hierarchical routing engine that maps URL paths to handlers via a nested tree structure. The framework includes a runtime-agnostic serverless adapter that translates diverse cloud provider events into a standard request and response interface. It also features a dedicated WebSocket server implementation for bidirectional real-time communication

Drogon is a high-performance C++ HTTP web framework and asynchronous web server designed for building web applications and REST APIs. It utilizes an event-driven, non-blocking architecture to handle concurrent HTTP and WebSocket connections, and it implements a model-view-controller structure to separate business logic from presentation. The framework includes an integrated C++ object-relational mapping system and database client for performing asynchronous operations with relational databases and Redis key-value stores. It supports real-time, full-duplex communication via WebSockets and prov

Iron is a Rust web framework used for building concurrent web applications and APIs. It functions as a concurrent HTTP server and provides a stateless route dispatcher to map incoming URL paths and globs to specific handler functions. The project is centered around a middleware-based request pipeline, which allows the request-response cycle to be extended via plugins and modifiers. It utilizes a thread-safe state container to store shared application memory accessible across all concurrent handlers and middleware. The framework covers broad capability areas including dynamic API routing, sta

Helidon is a Java microservices framework designed for building cloud-native applications. It provides a virtual thread web server to handle high-volume concurrent network requests and implements MicroProfile specifications, including JAX-RS and CDI, to ensure interoperability and standardization. The framework functions as a multi-protocol API gateway, supporting the delivery of data through REST, GraphQL, and gRPC. It includes a native compiler that transforms Java bytecode into standalone native executables to reduce memory footprint and startup time. The platform covers functional-reacti

GCDWebServer is a lightweight HTTP 1.1 server for iOS, macOS, and tvOS. It serves as an embedded network server for Apple platforms, allowing developers to handle incoming requests through custom synchronous or asynchronous handlers. The project includes a WebDAV server implementation for remote file management, directory browsing, and synchronization using standard network clients. It also provides a web-based file manager that enables users to upload, download, and organize files within an application sandbox via a browser. Additional capabilities include gzip compression, JSON processing,

This project is an event-driven PHP application server and HTTP server bridge that allows Laravel applications to run on a persistent engine. By keeping the application in memory, it eliminates the boot overhead typically required for every individual request to increase request speeds. The server includes an application state sandbox that isolates the application container between requests to prevent data leakage and state pollution. It also features a shared memory data store for retrieving information across multiple worker processes and provides a WebSocket server implementation for persi

Polka is a minimalist Node.js web framework and HTTP routing engine. It provides a small-footprint server implementation designed for low overhead, mapping URL paths and HTTP methods to specific handler functions. The project utilizes a middleware-based architecture, processing requests through a sequence of functions to handle tasks such as logging, authorization, and data modification. It allows for the organization of these functions into global and path-filtered groups to control execution order. The framework covers core web capabilities including route parameter extraction, request URL

This project is a software engineering educational resource providing a collection of canonical system implementations. It serves as a library of computer science case studies and polyglot code examples designed to demonstrate architectural tradeoffs and design patterns through concise versions of fundamental software components. The repository focuses on studying the implementation of core concepts such as consensus algorithms, interpreters, and database engines. It provides minimal versions of complex systems to facilitate the analysis of language design, data structure implementation, and