A fast and reliable ARQ protocol that helps applications to reduce network latency. [MIT]

A C++ non-blocking network library for multi-threaded server in Linux. [BSD]

A single file C++11 header-only HTTP/HTTPS server library. [MIT]

Extremely lightweight webserver. [GPL2]

An optimized HTTP server with support for HTTP/1.x and HTTP/2. It can also be used as a library. [MIT]

High-speed, modular asynchronous communication library. [LGPL3/MPL2] website

Streaming data platform for developers. Kafka API compatible. 10x faster. [BSL]

Facebook's collection of C++ HTTP libraries including an easy to use HTTP server. [BSD]

C++ REST SDK (previously named Casablanca). [Apache2]

C++/Boost Asio based websocket client/server library. [BSD]

A modern C++ HTTP requests library with a simple but powerful interface. Modeled after the Python Requests module. [MIT] website

A lightweight pure C WebSocket implementation that provides both client and server libraries. [LGPL2.1 + static link exception] website

HTTP/2 C Library. [MIT] website

C++ high performance networking with TCP/UDP/HTTP protocols. [BSD]

Data Plane Development Kit, libraries and drivers for fast packet processing. [BSD-3-Clause & GPL-2.0] website

A cross platform, open source, C++ networking engine for game programmers. [BSD]

A client/server application framework to build asynchronous, event-driven modern C++ services. [Apache-2.0]

An embeddedable library (and command line tool) aiming to transfer data between 2 systems as fast as possible over multiple TCP paths. [BSD-3-Clause]

Reliable UDP networking library. [MIT] website

a multiplatform C++ network sniffing and packet parsing and crafting framework. [Unlicense]

A portable C/C++ library for network traffic capture. [BSD] website

High-speed packet processing framework. [LGPL-2.1] website

HTTP server library in C designed to be lightweight and easy to use. [Apache2/GPL2]

Highly scalable user-level TCP stack for multicore systems. [Modified BSD]

C++11 Asynchronous RESTful framework. [AGPL]

A C library for asynchronous DNS requests. [MIT]

A tiny, primitive, fast HTTP request/response parser. [MIT]

A QUIC protocol library extracted from Chromium's QUIC Implementation. [BSD]

Simple REST client for C++. It wraps libcurl for HTTP requests. [MIT]

Ultra fast and low latency asynchronous socket server & client C++ library with support TCP, SSL, UDP, HTTP, HTTPS, WebSocket protocols and 10K connections problem solution. [MIT]

Asynchronous networking for C. [MIT]

A header-only C++14 library that gives you an embedded HTTP/Websocket server. [BSD]

A high-performance SIMD-accelerated RPC library on io_uring. [Apache2]

C++ library for creating an embedded Rest HTTP server (and more). [LGPL2.1]

HTTP/3 library written in C. [MIT] website

A portable MQTT C client for embedded systems and PCs alike. [MIT] website

Simple, small, C++ embeddable webserver with WebSockets support. [BSD]

A C language-based ultra-light software platform for scalable server-side and networking applications. Think node.js for C programmers. [GPL2]

An object oriented C++ wrapper for CURL(libcurl). [MIT]

An asynchronous web framework for C++ built on top of Qt. [LGPL2]

Single C file TLS 1.2/1.3 implementation, using tomcrypt as crypto library [BSD-2-Clause]

mailio is a cross platform C++ library for MIME format and SMTP, POP3 and IMAP protocols. [BSD]

Apache Kafka client library for C and C++. [BSD-2-Clause]

Strictly RFC 3986 compliant URI parsing and handling library. [BSD-3-Clause]

C++ client for making FTP requests. [MIT]

Event based, high-level C++14 peer-to-peer library. [EUPL-1.1 (OSI approved)]

URI parser/builder library for C++, compatible with RFC 3986 and RFC 3987. [Boost]

An OO Network Programming Toolkit in C++. [?MIT?]

A collection of open-source libraries for high level network programming. [Boost]

Multiprotocol file transfer library. [MIT/X derivate license]

GNU libmicrohttpd is a small C library that is supposed to make it easy to run an HTTP server as part of another application. [LGPL v2.1+]

Build high performance C++ HTTP servers without being a C++ expert. [MIT]

A lightweight TCP/IP stack. [Modified BSD]