(UDP: User Datagram Protocol User Datagram Protocol (UDP) is a connectionless transport layer protocol in the ISO reference model, which provides simple and unreliable transaction-oriented information transmission services. UDP protocol is basically the interface between IP protocol and upper layer protocol. UDP protocol is suitable for ports to distinguish multiple applications running on the same device. Since most network applications run on the same machine, the computer must be able to ensure that the software program on the destination machine can get the data packet from the source machine, and the source computer can receive the correct reply. This is done by using the "port number" of UDP. For example, if a workstation wants to use the domain name service system on workstation 128. 1.123.1,it will give the packet a destination address128.1and insert the destination port number 53 in the UDP header. The source port number identifies the application that the local machine requests domain name service, and all response packets generated by the destination station need to be assigned to this port of the source host. For a detailed introduction of UDP ports, please refer to related articles. Unlike TCP, UDP does not provide reliable mechanism, flow control and error recovery functions for IP protocol. Because UDP is relatively simple, the UDP header contains fewer bytes and consumes less load than TCP. UDP is suitable for situations where TCP reliability mechanism is not needed, for example, when high-level protocols or applications provide error and flow control functions.