Most network devices still got a serial console. If you got a Mac and want to connect to this console, get yourself a Serial-to-USB converter that is supported by Apple. A good one is the Keyspan usa-19hs. After you installed the driver, plug in the USB serial Adapter.
Now you could search and download some Terminal Software. But it is much easier. Use screen. screen is already built in. You have nothing to compile, nothing to add, just use it like this:
screen /dev/tty.Keyserial1 9600
When you finished your work just close screen with “ctrl-a k“.
Another method is the usage of cu.
sudo cu -l /dev/tty.Keyserial1 -s 9600
cu is easier to use, if you have to send a break signal.