PuTTY - Popular free terminal application. Mostly used as an SSH client.
TinyWall - Lightweight and non-intrusive firewall
MobaXterm - Enhanced terminal for Windows with X11 server, tabbed SSH client, network tools and much more
Windows 10 Firewall Control - Windows 10 Firewall Control: simple and exhaustive solution for applications network activity controlling and monitoring.
iTerm2 - A terminal emulator for macOS that does amazing things.
GlassWire - Visualize network activity in detail, get notified when new apps access the network, look out for...