The User Datagram Protocol (UDP) is a simple protocol used to send messages from one computer to another. The protocol assumes that the Internet Protocol (IP) is used as the underlying protocol to route packets of data (datagram) through the network. UDP does not set up a connection between the source and destination. It just pushes packets of data out on the network and accepts incoming datagrams at the receiver. UDP does not guarantee delivery or the correct order of arrival. UDP only provides the possiblity to use a checksum to check the integrity of the data at the receiver. Applications requiring ordered reliable delivery of streams of data should use the Transmission Control Protocol (TCP).

UDP is used to send messages to other programs with a minimum of overhead. This makes UDP much faster than TCP. UDP is used by application whereby speed is of more importance than correct delivery of the data. Applications which make use of UDP include chatting, instant messaging and video conferencing.

Communication between an application on a computer and UDP is through a UDP port. The combination of IP address and port number is called a socket. An application that is offering service waits for messages to come in on a specific port dedicated to that service. This makes it possible to have more than one UDP services running on a computer.

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