15.0 Introduction

In Chapter 12, "File I/O and Serialization," it was shown that in many cases, local data access ultimately found its way into the basic layers of the file classes. Whether you are creating an advanced Extensible Markup Language (XML) processing application, working with the latest database technology, or using a simple configuration scheme, the probability is high that the file classes will soon come into play whether you realize it or not. This chapter also serves as a starting point with a key difference. This time, you'll work with remote data.

The socket library is a low-level API designed to do one thing, communicate with a remote computer. How the communication is performed is left up to the server. Any clients that want to connect to the server must follow a set of rules to successfully interact. These sets of rules are generally standardized and published as protocols . Some of the better known protocols include the Hypertext Transfer Protocol (HTTP), File Transfer Protocol (FTP), Network News Transfer Protocol (NNTP), and the Simple Object Access Protocol (SOAP). This chapter looks at the underlying mechanics that each of these protocols utilize. Additionally, you'll see how you can easily create your own protocol as you work through the sample code to create a client- and server-based number-guessing game.