Pagekite.py is tool using reverse proxy to create a tunnel to your localhost which is then publicly accessible from outside your networks, and this is also known as localhost tunneling which is especially useful when you want to quickly test or access a local running web app behind NAT and firewall from outside of your networks and don't want to go through the complicated processes such as: buying a cloud-based server like vps for dns configuration with public static ip, or deployment to cloud based instances like aws ec2, and etc.

Ping is the most commonly-used tool for simply troubleshooting network connectivity.

Mac network traffic command line monitoring tool nettop.

IP address classes (Class A, B, C) and subnetting (CIDR).

OSI model and DoD (TCP/IP) model in computer networking.