TCP and UDP port

In the TCP and UDP protocols used in computer networking, a port is a special number present in the header of a data packet. Ports are typically used to map data to a particular process running on a computer.

Ports can be readily explained with an analogy: think of IP addresses as the street address of an apartment building, and the port number as the number of a particular apartment within that building. If a letter (a data packet) is sent to the apartment building (IP) without an apartment number (port number) on it, then nobody knows who (which service) it is for. In order for the delivery to work, the sender needs to include an apartment number along with the address to ensure the letter gets to the right domicile.

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