A port is a physical docking point using which an external device can be connected to the computer. It can also be programmatic docking point through which information flows from a program to the computer or over the Internet.
A network port which is provided by the Transport Layer protocols of Internet Protocol suite, such as Transmission Control Protocol (TCP) and User Diagram Protocol (UDP) is a number which serving endpoint communication between two computers.
To determine what protocol incoming traffic should be directed to, different port numbers are used. They allow a single host with a single IP address to run network services. Each port number have a distinct service, and for each host can have 65535 ports per IP address. Internet Assigned Numbers Authority (IANA) is responsible for managing the uses of these ports. There are three categories for ports by IANA −
Some well-known ports are −
|Port number||Transport protocol||Service name|
|20,21||TCP||File Transfer Protocol|
|25||TCP||Simple Mail Transfer Protocol(SMTP)|
|53||TCP and UDP||Domain Name System(DNS)|
|110||TCP||Post Office Protocol(POP3)|
|123||UDP||Network Time Protocol(NTP)|
1024 to 49151 – registered ports assigned by IANA to a specific service upon application by a requesting entity.
49152 to 65 535 – dynamic (private, high) ports range from 49,152 to 65,535. Can be used by private or customer service or temporal purposes.