Datagram Sockets (UDP)

Lesson 5 covered TCP sockets, which open a connection, guarantee ordered delivery, and retransmit anything that gets lost. UDP discards all of that. There is no connection, no ordering, no retransmission, and no flow control. The kernel receives a buffer with a destination address and ships it off. Whether it arrives, and in what order relative to other packets, is the network's problem. This lesson covers how to use UDP from Java with DatagramSocket and DatagramPacket, when this trade-off fits an e-commerce system, and the pitfalls that affect first-time UDP users.