In computer networking, the term port can refer to either physical or virtual connection points. In computer terms, a port generally refers to the female part of connection. Computer ports have many uses, to connect a monitor, webcam, speakers, or other peripheral devices.
On the Physical Layer
A computer port is a specialized outlet on a piece of equipment to which a plug or cable connects. Electronically, the several conductors where the port and cable contacts connect, provide a method to transfer signals between devices.
On the Transport Layer
A port is an application-specific or process-specific software construct serving as a communications endpoint in a computer’s host operating system. The purpose of ports is to uniquely identify different applications or processes running on a single computer and thereby enable them to share a single physical connection to a packet-switched network like the Internet. In the context of the Internet Protocol, a port is associated with an IP address of the host, as well as the type of protocol used for communication.
Ports are two types:
- Physical Ports
- Virtual Ports
Ports on Physical Layer (Physical Port)
Physical ports are used for connecting a computer trough a cable and a socket to a peripheral device. Physical computer ports list includes serial ports ( DB9 socket ), USB ports ( USB 2.0 or 3.0 socket / connector ), parallel ports ( DB25 socket / connector ), ethernet / internet ports ( RJ45 socket / connector ).
Physically identical connectors may be used for widely different standards, especially on older personal computer systems, or systems not generally designed according to the current Microsoft Windows compatibility guides. For example, a female 9-pin D-subminiature connector on the original IBM PC could have been used for monochrome video, color analog video (in two incompatible standards), a joystick interface, or for a MIDI musical instrument digital control interface. The original IBM PC also had two identical 5 pin DIN connectors, one used for the keyboard, the second for a cassette recorder interface; the two were not interchangeable. The smaller mini-DIN connector has been variously used for the keyboard and two different kinds of mouse; older Macintosh family computers used the mini-DIN for a serial port or for a keyboard connector with different standards than the IBM-descended systems.
Electronically, hardware ports can almost always be divided into two groups based on the signal transfer:
- Serial ports send and receive one bit at a time via a single wire pair (Ground and +/-).
- Parallel ports send multiple bits at the same time over several sets of wires.
Types of Physical Port
- Digital Visual Interface
- Display Port
- IEEE 1394 Interface (FireWire)
- PS/2 Connector
- Serial Port
- VGA Connector
Ports on Transport Layer (Virtual Port)
Virtual ports are data gates that allow software application (network) to use hardware resources without any interfering. This computer ports (network ports) are defined by IANA (Internet Assigned Numbers Authority) and are used by TCP (Transmission Control Protocol), UDP (User Datagram Protocol), DCCP (Datagram Congestion Control Protocol) and SCTP (Stream Control Transmission Protocol).
Virtual ports are part of TCP/IP networking. Range of Virtual Port are: 0 to 65535
Types of Virtual Port
- 20 & 21: File Transfer Protocol (FTP)
- 22: Secure Shell (SSH)
- 23: Telnet remote login service
- 25: Simple Mail Transfer Protocol (SMTP)
- 53: Domain Name System (DNS) service
- 80: Hypertext Transfer Protocol (HTTP) used in the World Wide Web
- 110: Post Office Protocol (POP3)
- 119: Network News Transfer Protocol (NNTP)
- 143: Internet Message Access Protocol (IMAP)
- 161: Simple Network Management Protocol (SNMP)
- 194: Internet Relay Chat (IRC)
- 443: HTTP Secure (HTTPS)
- 465: SMTP Secure (SMTPS)