microsoft/msquic

MsQuic is Microsoft's implementation of QUIC, a modern internet networking protocol standardized by the IETF. QUIC is a replacement for the older combination of TCP and TLS that most internet traffic uses today. It runs on top of UDP instead of TCP and bundles encryption into the protocol itself, which allows it to do things that TCP cannot, like surviving a change in the client's IP address mid-connection and starting to exchange data with zero extra round trips on repeat visits. In practical terms, QUIC is what powers HTTP/3, the latest version of the protocol your browser uses to load websites. MsQuic provides the library that other software can build on top of to send and receive data using QUIC. It is written in C for performance and low-level control, but it also exposes wrappers for C++, C#, and Rust so developers in those languages can use it without writing C directly. The library runs on Windows, Linux, and macOS. It is designed for both client and server roles and is optimized for high throughput and low latency. Features include asynchronous input and output, support for both reliable and unreliable data streams within a single connection, and kernel bypass via XDP on Windows for applications that need maximum performance. MsQuic is used in production inside several Microsoft products. The repository includes documentation for building the library, running tests, deploying it in real environments, and diagnosing network issues. A sample server and client application is included to help developers get started quickly.