Overview

In this chapter, I start by looking at what a protocol is, then I show how it can be implemented in software. I'll examine

• the definition of a protocol,

• the standard way of describing a protocol,

• the client server model,

• modal and modeless clients, and

• logical connections open, close, and data transfer

Because this is a hands-on book, I'll illustrate these points by creating a protocol from scratch (called SCRATCHP) and writing a utility that allows you to exercise the protocol. While implementing the protocol, you'll have an opportunity to explore the following areas.

• Storage of Ethernet and SLIP frames

• Ethernet addressing

• Protocol identification

• Byte swapping

• Low-level packet transmission and reception

You'll end up with a stand-alone utility that can be used to exercise the protocol that's been created, or it can be used as a base for implementing another protocol. The foundations will have been laid for the TCP/IP protocols to come.

Protocol

For two computers to communicate, they must speak the same language. A communication language framework is generally called a protocol. The name is derived from the framework employed by diplomats when attempting to communicate across cultural boundaries. Two computers may employ different processors, languages, and operating systems, but if they both use a common protocol, then they can communicate.

Protocols don't just enable communications, they also restrict them. Neither party may stray outside the bounds of protocol without facing incomprehension or rejection. So a protocol doesn't just define how communication may...