习惯了TCP编程，认为UDP可以包办这些问题是错误的。一个UDP应用程序要承担可靠性方面的全部工作，包括报文的丢失、重复、时延、乱序以及连接失效等问题。



通常我们在可靠性好，传输时延小的局域网上开发测试，一些问题不容易暴露，但在大型互联网上却会出现错误。



UDP协议把递送的可靠性责任推到了上层即应用层，下面简单编写了几个类来专门处理两个问题：乱序和丢包。-accustomed to the TCP programming, UDP can be arranged that these issues is wrong. A UDP applications to bear reliability of the entire work, including packet loss, duplication and delay, disorder and connectivity problems such as the failure. Usually we reliability, small transmission delay of LAN development and testing, some problems are not easily exposed. but the major Internet has an error occurs. UDP transmitted put the blame on the reliability of the upper level that is the application layer, following the preparation of a few simple categories devoted to the following two questions : disorder and packet loss.