Port (computing)
From Freepedia
In computing, a port (derived from seaport) is usually a connection through which data is sent and received. An exception is a software port (porting, derived from transport), which is software that has been "transported" to another computer system (see below for details). Image:Ibook-g3900-ports-lg.jpg
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Hardware Port
A hardware port is an electrically wired outlet on a piece of equipment into which a plug or cable connects. These hardware ports have different physical shapes such as male, female, round, rectangular, square, oblong, etc. There is some standardization to physical properties and function. For instance, most home computers have a keyboard port (currently round or telephone type), into which the keyboard is connected. Hardware ports can almost always be divided into two groups: One that sends and receives one bit at a time via a single wire pair (Ground and +/-) is called serial port(s). A port that sends multiple bits at the same time over several sets of wires is called a parallel port(s). The system bus that holds circuit cards for a computer "Mother Board (MO)" is a form of parallel port. Note: Light fiber, microwave, other technologies (i.e. quantum) may have special cases.
Hardware Port trunking (HPT) is a technology that allows multiple hardware ports to be aggregated into a single group, effectively creating a single connection with a higher bandwidth. This technology also provides a higher degree of fault tolerance. Compare to Software Port Trunking (SPT) where two agents (websites, channels, etc.)are bonded into one with the same effectiveness, i.e. ISDN B1 (64K) plus B2 (64K) equals data throughput of 128K.
Network port
A software network port is an identified doorway (address) for communicating between a program and another communications system or program often passing through a hardware port. The network port is usually numbered and a standard network implementation like TCP, UDP or IP (see below) will attach a port number to data it sends. The receiving implementation will guard and listen at the attached port number (doorway) to figure out which program to send data to on its system. A port may send/receive data one direction at a time (simplex) or simultaneously in both directions (duplex). These software network ports may also connect internal programs on a single computer system.
In TCP and UDP the combination of a port and a network address (IP-number) is called a socket: e.g. the list of well-known ports (computing).
I/O or machine port - port-mapped I/O
For Input or Output (I/O) operations nearly all processor families use similar assembly instructions for both memory access and hardware I/O (see memory-mapped I/O for details). However, Intel microprocessors have assembly instructions (IN and OUT) that are used specifically for hardware I/O. These instructions figure out which hardware device to communicate with using the concept of an I/O port or machine port. These ports are numbered based on which hardware device they refer to.
Intel microprocessors generally allow one octet (8-bit byte or word) to be sent or received during each instruction. The hardware device decides how to interpret data sent to it and what data to send to the processor. For example, a common use is to ask a hardware device which byte (in a data transfer) it will be sending next.
Software port
Software is sometimes written for specific processors, operating systems, or programming interfaces. Software porting is the act of changing such software to operate on a different system. The forming of the present participle (porting) is the correct usage and it is often abused, causing confusion without the "ing" in this case, thus a Software Port (see above) requires an address.
See also
- FireWire
- USB
- Bluetooth
- Wifi
- Parallel port
- Serial port
- List of well known network ports
- List of port numbers
