The operating environment of this tutorial: windows7 system and Dell G3 computer.

The transport layer of the Internet has two main protocols, which complement each other. Connectionless is UDP, which does almost nothing but send packets to applications and allow them to build their own protocols at the required level. Connection-oriented is TCP, which does almost everything.

UDP is the abbreviation of User Datagram Protocol, and its Chinese name is User Datagram Protocol. It is a connectionless transport layer protocol in OSI (Open Systems Interconnection) reference model, which provides simple and unreliable information transmission service oriented to transactions. IETF RFC 768 is the formal specification of UDP. The protocol number of UDP in the IP message is 17.

UDP protocol is used to process data packets, just like TCP protocol. In the OSI model, they are all located at the upper layer of the transport layer and IP protocol. The disadvantage of UDP is that it does not provide grouping, assembly and sorting of packets, that is, when a message is sent, it is impossible to know whether it arrives safely and completely. UDP is used to support network applications that need to transfer data between computers. Many client/server network applications, including network video conference system, need to use UDP protocol. UDP protocol has been used for many years since it came out. Although its initial glory has been covered by some similar protocols, UDP is still a very practical and feasible network transport layer protocol even today.

Many applications only support UDP, such as multimedia data streams, and do not generate any additional data, even if they know that there are damaged packets, they will not be retransmitted. UDP is the best choice when transmission performance is emphasized rather than transmission integrity, such as audio and multimedia applications. UDP is also a good choice when the data transmission time is so short that the previous connection process becomes the main body of the whole traffic.

Content:

UDP is a connectionless transport layer protocol in OSI reference model, which is mainly used for transmission that does not require the sequential arrival of data packets. The checking and sorting of data packet transmission sequence is completed by the application layer [4], which provides simple and unreliable information transmission service oriented to transactions. UDP protocol is basically the interface between IP protocol and upper layer protocol. UDP protocol is suitable for multiple applications running on the same device.

UDP provides connectionless communication, which does not guarantee the reliability of data packets, and is suitable for transmitting a small amount of data at a time. The application layer is responsible for the reliability of UDP transmission. Commonly used UDP port numbers are: 53(DNS), 69(TFTP), 16 1(SNMP), and the UDP protocols used are: TFTP, SNMP, NFS, DNS and BOOTP.

UDP message has no reliability guarantee, sequence guarantee and flow control fields, so its reliability is poor. However, it is precisely because UDP protocol has few control options, small delay and high data transmission efficiency in the process of data transmission that it is suitable for applications that do not require high reliability, or applications that can ensure reliability, such as DNS, TFTP, SNMP and so on.

Function:

In order to identify multiple destination addresses on a given host and allow multiple applications to work on the same host and send and receive data packets independently, a user datagram protocol UDP is designed.

UDP uses the underlying Internet protocol to transmit messages, and provides unreliable connectionless packet transmission services like IP. It does not provide functions such as message arrival confirmation, sequencing and flow control.

UDP Helper can relay and forward the broadcast message of the specified UDP port, that is, convert the broadcast message of the specified UDP port into unicast message and send it to the specified server, which plays the role of relay.