EIFFELNET MANUAL 

1 INTRODUCTION TO EIFFELNET

1.1 What is EiffelNet?

The client-server model of computing is quickly gaining ground as a way of optimizing network resources and of building sophisticated and flexible transactional applications.

The object-oriented method of software development, as embodied in Eiffel, potentially provides ideal support for developing client-server applications. The EiffelNet library described in this report makes this potential a reality by addressing one the crucial needs of client-server development: how to exchange objects between software systems. Systems using EiffelNet can exchange object structures with other systems running on the same machine or on different machines; in the case of different machines, the hardware architectures need not be the same. Objects are transmitted using sockets.

Writing client-server applications, especially their communication aspects, is an arduous task; developers must master many tricky details of socket programming and other low-level mechanisms. EiffelNet hides this complexity by providing ready-made classes addressing the most common cases, so that developers only have to describe what is specific to their application, letting EiffelNet handle the whole process of communication and synchronization between clients and servers. This part of EiffelNet is known as the predefined level and for many uses this is the only one that you will need to learn about. For developments requiring a finer degree of control, all the major mechanisms of socket programming are still accessible in a convenient form through more specialized classes.

In offering these varying levels of abstraction and control, EiffelNet follows the principles set by other libraries of the ISE Eiffel 3 environment (see for example the discussion of EiffelLex in reference [2]). Some users require a mechanism that will be very easy to learn and will hide all the details in common cases; other users (or the same at later stages of their work) need to access the whole array of facilities available at the level of the underlying hardware or software. The various components of the library should address all these needs.

This manual describes how to use EiffelNet at its various levels of abstraction.

1.2 Background and prerequisites

EiffelNet is a component of the ISE Eiffel 3 development environment. Please contact your ISE Eiffel distributor or ISE to find out how to acquire EiffelNet if it is not already part of your delivery.

This manual assumes the following prerequisites:

Familiarity with the basic Eiffel concepts: classes, inheritance, features, assertions, exception handling (see reference [1] in the bibliography).

Experience of writing software with Eiffel.

Basic knowledge of the EiffelBase libraries, as described in reference [2].

Familiarity with the basic concepts of client-server computing will also be helpful (see for example reference [3]); if you are new to this area, however, you will still be able to use EiffelNet, as this manual defines all the needed concepts.

1.3 Organization of this manual

Section 2 discusses the notion of client and server. Section 3 presents an overview of EiffelNet's facilities. Section 4 describes the predefined level: a set of high-level classes that provide a complete framework, covering the most common uses and limiting the developer's work to the strict minimum. Sections 6 to 10 describe the facilities in detail through a set of increasingly ambitious examples (whose texts may all be found in the directory $EIFFEL4/examples/net of the Eiffel distribution). Section 11 is a short bibliography.

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