View source for User Datagram Protocol

{{IPstack}}
The '''User Datagram Protocol''' ('''UDP''') is a core member of the [[Internet Protocol Suite]], the set of network protocols used for the [[Internet]]. With UDP, computer applications can send messages, known as ''[[datagram]]s'', to other hosts on an [[Internet Protocol]] (IP) network without needing other communications to set up special transmission channels or data paths. UDP is sometimes called the '''Universal Datagram Protocol'''. The protocol was designed by [[David P. Reed]] in 1980 and formally defined in [[Rfc:768|RFC 768]].
== Ports ==
{{main|List of TCP and UDP port numbers}}
UDP applications use [[datagram socket]]s to establish host-to-host communications. Sockets bind the application to service [[TCP and UDP port|ports]] that functions as the endpoints of data transmission. A port is a software structure that is identified by the port number, a 16 [[bit]] integer value, allowing for port numbers between 0 and 65,535. Port 0 is reserved, but is able to be used if the sending process does not expect messages in response.

Ports 1 through 1023 ([[hexadecimal]] 0x3FF) are named "well-known" ports and on [[Unix]]-like [[operating system]]s, binding to one of these ports requires [[superuser]] (root) access.

Ports 1024 through 49,151 (0xBFFF) are [[registered port]]s.

Ports 49,152 through 65,535 (0xFFFF)  are used as temporary ports usually by [[client (computing)|clients]] when communicating to [[server (computing)|servers]].
== Uses ==
There are many uses for UDP, for example [[BitTorrent]] optionally uses it for peer-to-peer file sharing. The [[Teredo tunneling]] protocol uses UDP.
== Further reading ==
* [[Rfc:768|RFC 768]], "User Datagram Protocol", J. Postel, August 1980
== Other websites ==
*[http://www.iana.org/assignments/port-numbers IANA Port Assignments]
*[http://condor.depaul.edu/~jkristof/papers/udpscanning.pdf The Trouble with UDP Scanning (PDF)]
*[http://www.networksorcery.com/enp/protocol/udp.htm Breakdown of UDP frame] {{Webarchive|url=https://web.archive.org/web/20090122022734/http://networksorcery.com/enp/protocol/udp.htm |date=2009-01-22 }}
*[http://msdn.microsoft.com/msdnmag/issues/06/02/UDP/ UDP on MSDN Magazine Sockets and WCF]


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[[Category:Internet protocols]]
[[Category:Internet standards]]