Chapter 2. Basic Network Concepts

This chapter covers the background networking concepts you need to understand before writing networked programs in Java (or, for that matter, in any language). Moving from the most general to the most specific, it explains what you need to know about networks in general, IP and TCP/IP-based networks in particular, and the Internet. This chapter doesn’t try to teach you how to wire a network or configure a router, but you will learn what you need to know to write applications that communicate across the Internet. Topics covered in this chapter include the definition of network, the TCP/IP layer model, the IP, TCP, and UDP protocols, firewalls and proxy servers, the Internet, and the Internet standardization process. Experienced network gurus may safely skip this chapter.


A network is a collection of computers and other devices that can send data to and receive data from each other, more or less in real time. A network is often connected by wires, and the bits of data are turned into electromagnetic waves that move through the wires. However, wireless networks transmit data through infrared light and microwaves, and many long-distance transmissions are now carried over fiber optic cables that send visible light through glass filaments. There’s nothing sacred about any particular physical medium for the transmission of data. Theoretically, data could be transmitted by coal-powered computers that send smoke signals to each other. The response ...

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