Back in 2018, Valve open-sourced their Steam networking sockets library as a basic network transport layer for games. This library is used by games from Counter-Strike to Dota 2 and since its public open-source drop has been picked up elsewhere. Finally after going nearly four years without a new version, GameNetworkingSockets v1.5 dropped today.
GameNetworkingSockets serves reliable and unreliable message types and provides a connection-oriented API for games/engines that is message-oriented like UDP. GameNetworkingSockets supports IPv6, peer-to-peer networking, encryption, and much more. It's been good enough for Valve's flagship game titles.
The last release until now of GameNetworkingSockets was v1.4.1 back in June 2022 while thankfully today is the debut of GameNetworkingSockets v1.5. This new version has a number of API additions as well as providing initial Rust bindings. That Rust binding support for GameNetworkingSockets comes via the open-source community rather than Valve developers.
The new version also has peer-to-peer (P2P) improvements, improved CMake integration, various compiler and platform compatibility fixes, security fixes, and a variety of other improvements. There is also better continuous integration (CI) testing now happening with GameNetworkingSockets.
Those interested in this open-source Valve networking library can find all of the code on GitHub under a BSD 3-clause license.