Top 4 port-knock open source projects

Hybrid Port Knocking System

A web client port-scanner written in GO, that supports the WASM/WASI interface for Browser WebAssembly runtime execution.

Layer 4 Single Packet Authentication Linux kernel module utilizing Netfilter hooks and kernel supported Berkeley Packet Filters (BPF)

A minimal tool that hides your online assets from online security scanners, researchers and hackers.