>This was easy because in those early days the Network Control Program known as NCP (this was before TCP/IP) would broadcast messages called RSTs to every possible host address on the network when they booted.

Note that NCP used 8 bit host addresses, so it wasn't as if you couldn't write a program to connect to all 256 possible addresses and see if a computer answered. But that would be rude.

https://en.wikipedia.org/wiki/Network_Control_Program

The author's top level web page says:

https://iconia.com/

>from the keyboard of geoff goodfellow

I'm glad to learn that Geoffrey has finally upgraded his tty to a real keyboard! He used to always use this From address:

https://iconia.com/TELECOMDigestV2.33.txt

From: the tty of Geoffrey S. Goodfellow