The Communication port is a physical or logical endpoint for the exchange of information between a computer and another device. The term can refer to two distinct concepts. Firstly, it can mean a physical interface on a piece of hardware. This includes physical connectors like a USB port, an Ethernet (LAN) port, a serial COM port (using a DE-9 connector for RS-232C), or a GPIB port. These physical ports are the hardware gateways through which data signals enter and leave the device. For example, to control a power supply via USB, you must connect a USB cable to the USB ports on both the computer and the power supply.
Secondly, in the context of TCP/IP networking (used by Ethernet/LAN), a "port" is a logical, numbered endpoint within an operating system. These are not physical but are used to identify a specific process or service. When data arrives at a computer's IP address, the port number tells the operating system which application to deliver the data to (e.g., web traffic to port 80, secure web traffic to port 443).
LXI-compliant instruments, for instance, use specific TCP/IP port numbers for communication protocols like VXI-11 (port 111) or SCPI-RAW (often port 5025). Therefore, establishing remote communication with a power supply involves both a physical connection (the cable and hardware port) and, for network-based control, a logical connection (the IP address and software port number).