A packet tracer is a network simulation tool developed by Cisco that allows users to create, configure, and troubleshoot network topologies without the need for physical hardware. It provides a graphical user interface where you can drag and drop devices like routers, switches, and computers to build a network. Users can simulate data traffic, configure device settings, and visualize how data packets travel through the network. Packet Tracer is often used in educational settings to help students learn networking concepts and practice skills in a safe environment. It's a great way to experiment with networking configurations and understand how different devices interact.

HOST $=127\mathrm{.}0\mathrm{.}0\mathrm{.}1$

PORT $=4444$

PORT $=5555$