One of the first technical books I ever bought was The RS-232 Solution. It dealt in a clear way with the details of data transmission over serial connections, and in those days I dealt with such connections a lot. The book told me what I was looking at when I opened the cover on a connector, put me on the path to understanding how to use a breakout box, and saved me, my employer, and our customers a great deal of time.
Then I changed jobs, and the details of serial cables were no longer my problem. But presently I spent a lot of time looking at the details of "terminfo" and "termcap" and considering how to make this or that type of terminal behave when connected to this or that type of computer. I believe that I invested in the book Terminfo and Termcap, but perhaps not. I did manage to make some off-brand terminals behave better than they might have.
Then I changed jobs again, and really didn't spend a lot of time thinking about terminal emulation. On the whole, I didn't miss it.
This afternoon, I wasted several hours of my time and a tech support rep's. First, I wasted a few minutes of my own looking for the proper cable--null modem, female and nine-pin (or if you will, nine-socket) at both ends. Then I wasted the hours because I could not get a machine to boot into the proper system,. This was largely, as far as I can tell, because the terminal emulation program was throwing away or otherwise mis-handling my keystrokes. This machine wasn't manufactured--I don't suppose its manufacturer was incorporated--when I last looked at terminal emulations.
I will add that when I first dealt with RS-232, 9600 Bps was considered a fast connection. WiFi can in theory do roughly 700 times that. In other words, for every second a web page takes to load over a good WiFi connection, it would take about twelve minutes at 9600 Bps. I remember the author of The RS-232 Solution writing of 200-Bps connections "but in those days it seemed like magic." Indeed.