What is the hardware implementation of a port and/or network socket?

I understand that, at the lowest level, x86 uses opcodes such as IN and OUT when the data resulting from the instruction execution is to be sent to a peripheral with a port-mapped I/O memory address. Am I making an incorrect assumption that the port-mapped I/O memory addresses are synonymous with ports identified for networking? Whenever I read about the use of ports, the application has been abstracted far past the physical layer and it is difficult to draw a connection between the host hardware and their use in networking.

2 Answers 2


There is no hardware implementation of a TCP or UDP port or a network socket. That is like asking for a hardware implementation of an IP address. Ports are layer-4 addresses, and they are conceptual. A port represents a software connection between a layer-4 protocol and an application. A network socket consists of a combination of source and destination layer-3 (e.g. IP) and layer-4 (e.g. TCP) addresses.


All modern interfaces use DMA transfers. The IN/OUT opcodes are ancient, mostly used in the 16-bit era. Those hardware registers aka I/O ports have nothing to do with network ports as in hardware interfaces (ie. where you plug a cable into).

You might also be referring to TCP or UDP ports which are yet something different. These are subaddresses of a host that services are bound to (like TCP 80 for a HTTP web server or TCP 25 for an STMP mail server).

  • Good to know about the DMA. I was aware of that but reading more about it gives me a much better understanding of what's going on. Thanks! Commented Jul 16, 2017 at 0:06

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