aria2 is a lightweight multi-protocol & multi-source download utility
Fast cross-platform HTTP benchmarking tool written in Go
A cross-platform asynchronous HTTP(S) proxy server in C#
Lightweight service virtualization/ API simulation / API mocking tool
Fluent URL builder and testable HTTP client for .NET
A Promise based REST and HTTP client for Unity
Cross-platform C++ libraries with a network/internet focus.
a powerfull c++ library for win32/linux, server framework, HttpServlet