Reliable UDP networking library

Highly portable C system library: threads and synchronization primitives, sockets (TCP, UDP, SCTP), IPv4 and IPv6, IPC, hash functions (MD5, SHA-1, SHA-2, SHA-3, GOST), binary trees (RB, AVL) and more. Native code performance.

BACnet Protocol Stack library provides a BACnet application layer, network layer and media access (MAC) layer communications services.

Paul's PPP Package: PPP daemon and associated utilities | Official GitHub repo: https://github.com/ppp-project/ppp

SIIT and NAT64 for Linux

A high-performance socks5 server for Unix (Linux/Android/BSD/macOS/iOS)

nftables load balancer

IPv6 address rate limiting evasion tool (that also supports IPv4)

A library for fast IP address lookup in Python.

Simple multicast testing application

Lightweight UDP sockets abstraction for rapid implementation of message-oriented protocols

"TCMPortMapper.framework" is a clean and nice Objective-C API to provide knowledge about and improve the reachability of your machine from the big bad internet. "Port Map.app" is a nice standalone sample app using the framework to display reachability and enable setup of Port Mappings if your router allows for it.

A compact, reliable, high-performance TCP/IP protocol stack. Features dual IPv4 and IPv6 support, an SSL/TLS socket option, and support for Ethernet, Wi-Fi, and PHY controllers.

A improved fork of ENet, a tried and true networking library. C, C++, C# compatible.

Packetgraph library is a collection of network bricks you can connect to form a network graph.

Classic msend and mreceive tools for multicast testing. TIP: check out mcjoin(!) and mping as well.

A redsocks-like transparent IPv4/IPv6 TCP-to-SOCKS5 redirector (for Linux only)

Longest Prefix Match (LPM) library

Link-Local Multicast Resolution (LLMNR) Daemon for Linux

ipv6calc