在局域网中，管理员常常需要将某条信息发送给一组用户。如果使用一对一的发送方法，虽然是可行的，但是过于麻烦，也常会出现漏发、错发。为了更有效的解决这种组通信问题，出现了一种多播技术（也常称为组播通信），它是基于IP层的通信技术。资料介绍了多播的概念和一个编程实例。-In the local area network, an administrator often needs to be a message sent to a group of users. If you use the Send method of one-on-one, although it is feasible, but too much trouble, there will be leakage often made, mistakes made. In order to more effectively address the issue of group communication, there is a multicast technology (often referred to as multicast communication), which is based on the IP layer of the communication technologies. Information on the concept of a multicast and a programming example.