3.6. Overview of Ports and Sockets

On a TCP/IP network, data travels from a port on the sending computer to a port on the receiving computer. A port is a numerical value that identifies the application associated with the data. The source port number identifies the application that sent the data, and the destination port number identifies the application that receives the data. Each port is assigned a unique 16bit number in the range of 0 through 65535. Additionally, there are two types of ports—TCP and UDP—which are based on their respective protocols. Both TCP and UDP maintain a separate list of used (reserved and allocated) port numbers. This allows them both to make sure no port is duplicated within each list. A benefit of this mechanism ...

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