====== Port Number ======

Port numbers identify the each end of a network communication link and are established when the [[client]] opens a [[socket]] to connect to a [[server]]. Each port number must be unique within each host. The server processes for well-known [[application protocol|application protocols]] also have well-known port numbers (so the client can connect to them easily). For example [[HTTP]] uses port 80, [[FTP]] uses port 21 for control and port 20 for data, [[telnet]] uses port 23, [[SMTP]] port 25, etc. Clients will typically be assigned port numbers in the range 1024--65,536 at random by the host operating system. For a full list of the well known port numbers see the [[http://www.iana.org/assignments/port-numbers|list]] published by the Internet Assigned Numbers Authority (IANA) or the more user-friendly list maintained on [[wp>List_of_TCP_and_UDP_port_numbers|Wikipedia]]. //See also//: [[socket]].
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