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Port (computer networking)
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<p>In <a href="/facts/Computer_network/3w5RM99p">computer networking</a>, a port is a communication endpoint. At the software level within an <a href="/facts/Operating_system/8XTuvMh2">operating system</a>, a port is a logical construct that identifies a specific <a href="/facts/Process_(computing)/Vcq7EnUV">process</a> or a type of <a href="/facts/Network_service/GdLvd2ml">network service</a>. A port is uniquely identified by a number, the port number, associated with the combination of a <a href="/facts/Transport_protocol/UmIGUCeK">transport protocol</a> and the network <a href="/facts/IP_address/z9V22Sw9">IP address</a>. Port numbers are 16-bit <a href="/facts/Unsigned_integer/zWabo5M9">unsigned integers</a>. </p><p>The most common transport protocols that use port numbers are the <a href="/facts/Transmission_Control_Protocol/WW4sPrt9">Transmission Control Protocol</a> (TCP) and the <a href="/facts/User_Datagram_Protocol/dxLU0D6q">User Datagram Protocol</a> (UDP). The port completes the destination and origination addresses of a message within a <a href="/facts/Host_(network)/HPNcFXHk">host</a> to point to an operating system process. Specific port numbers are reserved to identify specific services so that an arriving packet can be easily forwarded to a running application. For this purpose, port numbers lower than 1024 identify the historically most commonly used services and are called the <a href="/facts/Well-known_port_numbers/c30Xg4d4">well-known port numbers</a>. Higher-numbered ports are available for general use by applications and are known as <a href="/facts/Ephemeral_port/Tls92nHS">ephemeral ports</a>. </p><p>Ports provide a <a href="/facts/Multiplexing/YE7hK8cw">multiplexing</a> service for multiple services or multiple communication sessions at one network address. In the <a href="/facts/Client%25E2%2580%2593server_model/FSnf27C5">client–server model</a> of application architecture, multiple simultaneous communication sessions may be initiated for the same service. </p>