Local servers are abundantly useful in offices, homes, and other areas with a lot of technology. I've personally created a few for my phone and laptop. They're extremely under accredited when compared to much larger systems that host publicly. Local servers are great for managing employees, wirelessly and effortlessly sending data between computers over a network, hosting a local website for easier control over what's happening, and much more.
For servers & clients, I use Python to connect clients to the server through the IP and port. For web servers, I use Python's Flask library for ease of use and management. Any data handled will be properly stored in an assorted and encrypted file system.