PS/2 is an older port type that was predominately used for input devices like keyboards and mice. Lightning is a newer technology used primarily in Apple products. Firewire is not a likely answer, input devices for firewire is rare/nonexistent. Bluetooth is not likely to be supported on a server, especially an old server.
The PS/2 port is a 6-pin mini-DIN connector used for connecting keyboards and mice to a PC compatible computer system Its name comes from the IBM Personal System/2 series of personal computers, with which it was introduced in 1987 The PS/2 mouse connector generally replaced the older DE-9 RS-232 "serial mouse" connector, while the PS/2 keyboard connector replaced the larger 5-pin/180° DIN connector used in the IBM PC/AT design The PS/2 keyboard port is electrically and logically identical to the IBM AT keyboard port, differing only in the type of electrical connector used The PS/2 platform introduced a second port with the same design as the keyboard port for use to connect a mouse