Port (computing)
In computing, port has several possible meanings. Which meaning is intended can usually be determined from context.
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2 Networking Port 3 Software Port 4 Machine or I/O Port 5 External link |
A hardware port is an outlet on a piece of equipment into which a plug or cable connects. For instance, a computer may have a keyboard port, into which the keyboard is connected.
A networking port, so named by analogy with the above, is a notational point for the connection of network programs. In TCP and UDP, multiple network services running on a single host are distinguished by port numbers; the operating system kernel uses these port numbers to sort out which packets should go to which programs. A program which is using a port, whether to await connections (i.e. to be a server) or to make connections, is said to have a socket bound to that port -- more hardware analogy. A well known port is between the range 0-1023 which were traditionally assigned by IANA. Ephemeral ports are somewhere between 1024 to 65535 depending on the implementation of the TCP/IP stack of an operating system.
List of some well known network ports:
In programming, a port is a localization or translation of a piece of software to a particular API, operating system, or generally any other computing environment than that for which it was written. See porting for detail.
A machine port, or I/O port is a concept peculiar to Intel microprocessors. It is the primary method for microprocessor control of hardware devices. A machine port is essentially equivalent to a single-byte memory location, except that reading from it or writing to it will have an effect defined by the device in question. For example, a common use is to provide a status register, where writing to the port will determine which of up to 256 bytes will be returned by the next read operation. Unlike other architectures, Intel-based computers primarily use DMA for bulk information transfer, not control.
See also: Memory-mapped I/OHardware Port
Networking Port
Software Port
Machine or I/O Port
