A client and server need to exchange information via messages. TCP and UDP provide the transport mechanisms to do this. The two processes also need to have a protocol in place so that message exchange can take place meaningfully.
Messages are sent across the network as a sequence of bytes, which has no structure except as a linear stream of bytes. We address the various possibilities for messages and the protocols that define them in the next chapter. In this chapter, we concentrate on a component of messages—the data that is transferred.
A program will typically build complex data structures ...
