It might seem at first glance that UDP is poor relative of TCP. So is there anything that UDP can do that TCP cannot? What is special about UDP is the fact that the destination of a UDP datagram does not have to be just a unique IP address, i.e., the network interface of a particular computer. The destination might also be a multicast; even a broadcast as well.
Though broadcasts can be addressed, addressing multicasts is much more interesting. For example, each client establishes a connection with the server in the Real Audio application. On the other hand, in the Progressive Real Audio application, the data is transmitted via multicasts, i.e., a huge amount of the transmission path capacity is saved. This is exactly the case where the UDP protocol serves you best.