Computer port (software)

For software socket port information, see Port number

For porting software to other computer systems, see Porting.

For other uses of "port", see port (disambiguation).

In computer programming, port has a wide range of meanings.

A software port (usually just called a 'port') is a virtual/logical data connection that can be used by programs to exchange data directly, instead of going through a file or other temporary storage location. The most common of these are TCP and UDP ports(ranges: 0-65535), which are used to exchange data between computers on the Internet.

In Flow-based programming, a 'port' is a (named) point of contact between a process and a connection.

I/O or machine port mechanism

A port number is part of the addressing information used to identify the senders and receivers of messages. Port numbers are most commonly used with TCP/IP connections. Home network routers and computer software work with ports and sometimes allow you to configure port number settings. These port numbers allow different applications on the same computer to share network resources simultaneously. For Input or Output (I/O) operations, nearly all processor families use memory-mapped I/O—the same assembly instructions are used for both memory access and hardware I/O. However, Intel microprocessors use port-mapped I/O—they have a completely separate set of assembly instructions (IN, INS, OUT, and OUTS) 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. These hardware I/O ports are in a completely different address space from normal memory.

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.

Some I/O ports are connected with "peripheral" devices outside the CPU itself, but inside the computer case. Other I/O ports are connected to "peripheral" external devices outside the computer case using some Computer port (hardware).

See also

• Port number
• Computer port (hardware)
• TCP and UDP port
• List of TCP and UDP port numbers