Java Network Programming (3rd ed) [Electronic resources] نسخه متنی

Chapter 13. UDP Datagrams and Sockets

Previous chapters discussed
network applications that use the TCP protocol. TCP is designed for
reliable transmission of data. If data is lost or damaged in
transmission, TCP ensures that the data is resent; if packets of data
arrive out of order, TCP puts them back in the correct order; if the
data is coming too fast for the connection, TCP throttles the speed
back so that packets won't be lost. A program never
needs to worry about receiving data that is out of order or
incorrect. However, this reliability comes at a price. That price is
speed. Establishing and tearing down TCP connections can take a fair
amount of time, particularly for protocols such as HTTP, which tend
to require many short transmissions.

The User Datagram Protocol (UDP) is an alternative protocol for
sending data over IP that is very quick, but not reliable. That is,
when you send UDP data, you have no way of knowing whether it
arrived, much less whether different pieces of data arrived in the
order in which you sent them. However, the pieces that do arrive
generally arrive quickly.