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Dec 4, 2023 · Source port numbers are randomly generated and are used to track different conversations. Destination port numbers identify specific services by using either a default port number for the service or a port number that is assigned manually by a system administrator.
Jan 25, 2024 · For instance, HTTP transfers use port number 80, whereas Telnet uses 23. As it is known, a device (i.e., computer) is identified by its IP address. Since multiple services (tabs) or applications run by web browsers simultaneously, to run network applications, the IP address alone is not sufficient.
Learn how data is encapsulated and decapsulated in the TCP/IP and OSI models, and what are the terms and roles of each layer. The web page does not explain how port numbers are used in the TCP/IP encapsulation process.
The use of ports and their identifying numbers are an extension to the addressing scheme. Once the address is used to deliver data to the wanted host on the network, the port number is used to identify the process for which the data is used. This enables one host to provide more than one service.
To transfer the file, the Transmission Control Protocol ( TCP) software layer in local host identifies the port number of 21, which, by convention, associates with an FTP request -- in the 16-bit port number integer that is appended to the request.
This Transport Layer header contains a Source Port Number and a Destination Port Number. The Port Numbers identify the application from which the data was received or is destined to. Read more on port numbers later in this article.
TCP and UDP specify the source and destination port numbers in their packet headers and that information, along with the source and destination IP addresses and the transport protocol (TCP or UDP), enables applications running on hosts on a TCP/IP network to communicate.
