2. 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, the user datagram protocol UDP is designed.
3.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.
4.UDPHelper can relay and forward the broadcast message of the specified UDP port, that is, the broadcast message of the specified UDP port is converted into a unicast message and sent to the specified server, which plays the role of relay. Extended data:
Characteristics of UDP protocol: 1. Because no connection is established when transmitting data, there is no need to maintain the connection status, including receiving and sending status, so a server can transmit the same message to multiple clients at the same time. 2. The header of 2.UDP packet is very short, only 8 bytes. Compared with TCP's 20-byte packet, UDP has little overhead. 3. Throughput is not controlled by congestion control algorithm, but only limited by data generation rate, transmission bandwidth of application software and performance of source host and terminal host. 4.UDP is message-oriented. The message handed over to the application by the sender UDP will be transmitted to the IP layer after the header is added. The boundaries of these messages remain unchanged, rather than being split or merged, so the application needs to choose the appropriate message size.