Ports explained!

Hi folks, have not posted lately was busy with some personal commitments, today we would talk about networking ports.

In computer networking, a port number is part of the addressing information used to identify the senders and receivers of messages. Some of the 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. Port numbers are mainly used with TCP/IP connections.

In technical terms: In computer networking a port is an application-specific or process-specific software construct serving as a communications endpoint in a computer’s host operating system. A port is associated with an IP address of the host, as well as the type of protocol used for communication.

A port number is a 16-bit unsigned integer, thus ranging from 0 to 65535. A process associates its input or output channels via Internet sockets, a type of file descriptors, with a transport protocol, a port number and an IP address. This process is known as binding, and enables sending and receiving data via the network.

The port numbers are encoded in the transport protocol packet header, and they can be readily interpreted not only by the sending and receiving computers, but also by other components of the networking infrastructure. In particular, firewalls are commonly configured to differentiate between packets based on their source or destination port numbers.

The practice of attempting to connect to a range of ports in sequence on a single computer is commonly known as port scanning. This is usually associated either with malicious cracking attempts or with network administrators looking for possible vulnerabilities to help prevent such attacks.

How it works

Port numbers work like telephone extensions. Just as a business telephone switchboard can use a main phone number and assign each employee an extension number (like x100, x101, etc.), so a computer has a main address(IP Address) and a set of port numbers to handle incoming and outgoing connections.

Uses in URL’s

Port numbers can occasionally be seen in the Uniform Resource Locator (URL) of a website or other services. By default, HTTP uses port 80 and HTTPS uses port 443, but a URL like http://www.example.com:8000/path/ specifies that the web site is served by the HTTP server on port 8000.

Commonly used ports

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)

443: HTTP Secure (HTTPS)

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