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The term 'port' is commonly used in the software and hardware worlds in the sense of a 'portal', i.e. way into or out off somewhere. A communications port is a way to communicate information into or out of some 'device'. Note that device here is used broadly. It could be some server out on the internet just as easily as a hardware box in your closet. So communications ports (or comm ports as they are generally called in short), are means by which some device can be talked to by some other device. In our case, the other device is CQC itself.
There are various types of comm ports, the most common of which are listed here:
- Serial port. This is an older but still widely used, inexpensive and reliable means of communications between devices. They come in a few variations, such as RS-232, RS-422, and RS-485. Most devices are RS-232, which is a simple, direct connection between two devices, as apposed to a network where multiple devices are connected to the same wire. It's not terribly fast, but more than fast enough for most devices.
- Ethernet. Your home network uses a system called Ethernet, and every personal computer has an Ethernet port these days. Though it's far less common than serial ports, more and more devices are also beginning to integrate Ethernet ports as well. It's more expensive and complex, so it tends to be on larger and more expensive devices. It's very fast.
- USB (Universal Serial Buss). USB is fairly ubiquitous these days on personal computers as well. It is also very fast, but like Ethernet it's more complex to implement so it's not as common as serial ports either. Some devices use USB to serial converters internally, so they can provide a serial port and a USB port, and you can use either one, or they provide a USB port and you run a driver on the computer that makes it look like a serial port to the software, since many control systems don't directly support USB.
- Infrared. Many devices that are less expensive will only support Infrared communications, i.e. they can only be controlled by an IR remote control. This is a one way only communications method, so there's no way to know if the operation worked, or to get information back from such devices. But systems like CQC can learn and spit back out IR commands and therefore control IR-only devices.
There are other options, but these are far and away the most common. Just because your device has one of these ports though doesn't necessarily mean that it can be controlled. Sometimes these ports are for future use or only for uploading new software into the device, not for control purposes.