Why port number is used

A port number primarily aids in the transmission of data between a network and an application. Port numbers work in collaboration with networking protocols to achieve this. Similarly, all outgoing network packets contain application port numbers in the packet header to enable the receiver to distinguish the specific application.

Port numbers are mainly used in TCP and UDP based networks, with an available range of 65, for assigning port numbers. By: Justin Stoltzfus Contributor, Reviewer. By: Satish Balakrishnan. Dictionary Dictionary Term of the Day. Natural Language Processing. Techopedia Terms. Connect with us. Save Article. Improve Article. Like Article. Next Difference between Physical and Logical Topology.

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Then, the data is sent back over the same port and displays in the program that supports that port the web browser. The network hardware and the software automatically process port numbers. Casual users of a network do not see these port numbers and don't need to take any action involving their operation. Individuals can, however, encounter network port numbers in certain situations. Network administrators may need to set up port forwarding to allow the port numbers of specific applications to pass through a firewall.

On home networks, a broadband router supports port forwarding on its configuration screens. A common application of homeport forwarding is for online games that use non-standard ports that the router's built-in firewall blocks.

Network programmers sometimes need to specify port numbers in their code, such as in socket programming.

This is usually seen in software development environments more than in mainstream consumer usage. Network security enthusiasts also frequently discuss the port number used as a key aspect of attack vulnerabilities and protections.

Ports can be classified as either open or closed. Open ports have an associated application that listens for new connection requests, and closed ports do not. A process called network port scanning detects test messages at each port number to identify which ports are open. Network professionals use port scanning as a tool to measure exposure to attackers and often lock down networks by closing non-essential ports. Hackers, in turn, use port scanners to probe networks for open ports that may be exploitable.

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