1 first, look at the English abbreviations of TCP/UDP, and you can see that they all have a P letter, which means that they all represent the rules of a protocol. Unicast, broadcast and multicast represent the form of data "playing" in the network, which refers to the difference between being heard by one person, being heard by a specific group of people or being heard by everyone. UDP supports unicast, multicast and broadcast, while TCP does not support broadcast. 2. Theoretically, the connection between routers should use crossover lines. 3. The web program you use and all the data you submit are stored on Baidu's server, and the administrator can make unlimited changes to any content in various ways. In most cases, different users have different permissions to manipulate data, because it is the safest for both programs and data. Let me briefly talk about the difference between TCP and UDP: 1. Connection based and connectionless 2. Requirements for system resources (more TCP, less UDP) 3. UDP program structure is relatively simple 4. Streaming mode and datagram mode 5. TCP guarantees the correctness of data, UDP may lose packets, TCP guarantees the order of data, and UDP does not. In addition, combined with the situation of GPRS network, let's talk about their differences: 1. There is a certain delay in TCP transmission, which is about 1600MS (provided by mobile), and the response speed of UDP is slightly faster. 2。 TCP header structure Source port 16-bit destination port 16-bit serial number 32-bit response serial number 32-bit TCP header length 4-bit reserved 6-bit control code 6-bit window size 16-bit offset 16-bit checksum 16-bit option 32-bit (optional). In this way, we get the minimum size of TCP header, which is 20 bytes. UDP header structure, the source port 16-bit destination port 16-bit length 16-bit checksum 16-bit UDP packet is much smaller. Indeed, because UDP is an unreliable connection, the original intention of the design is to send packets as soon as possible. Therefore, UDP protocol is very simplified.