What is Client-Server Architecture?

Server-client, Client-Server (C / S) structure. The C / S structure usually adopts a two-layer structure. The server is responsible for data management, and the client is responsible for completing interaction tasks with the user.

Server-Client, Client-Server (

The development of the C / S model has gone from a two-layer structure to a three-layer structure.

The two-tier structure consists of two parts: the front end is the client, which mainly completes the user interface display, accepts data input, verifies the validity of the data, sends requests to the back-end database, accepts the returned results, and processes the application logic; the back end is the server, which runs the DBMS , To provide database query and management.

The two-tier structure has some shortcomings: it is mainly manifested in: poor scalability of the system; difficulty in interoperability with other systems; difficulty in supporting multiple heterogeneous databases; frequent interaction between client programs and server-side DBMSs, and large network communication; all customers All computers need to install and configure the database client software, which is a very complicated task, etc.

Based on the above shortcomings of the two-tier structure, the three-tier structure has risen with the maturity of middleware technology. The core concept is to use middleware to divide the application into three different processing layers: the presentation layer, the business logic layer, and the data storage layer.

The three-tier structure has certain advantages over the two-tier structure: it has good openness; it reduces the cost of the entire system and is very convenient to maintain and upgrade; the system has good scalability; the system is simple to manage and can support heterogeneous databases. Usability; allows for tight security management ^[2]

Comparison of hardware environments

CS is built on the basis of local area network, and the special network server provides connection and data exchange services between the local area networks. In the CS structure, both the client and server need to process data tasks, which places higher requirements on the client's hardware. The BS structure is built on a wide area network and does not need to be equipped with a special network hardware environment. Although the hardware requirements of the client are not very high, only the operating system and browser need to run, but the server needs to process a large amount of real-time data, which puts higher requirements on the server hardware. Generally speaking, the BS structure can greatly reduce the cost compared to the CS structure. ^[1]

Comparison of system maintenance and upgrade

Each client in the CS structure must install and configure related software, such as operating system, client software, and so on. When the client software needs to be maintained and upgraded, even if only a certain function is added or deleted, all the client software in the CS structure needs to be uninstalled and reinstalled one by one. If you do not upgrade, you may encounter inconsistent client software versions and fail to work. Each client in the BS structure can process all kinds of information just through a browser, without the need to install client software.Almost all tasks such as maintenance and upgrade are performed on the server.If the system needs to be upgraded, only Install the upgrade program on the server.

Comparison of system security

The CS structure adopts a point-to-point structure model, and the data processing is based on a highly secure network protocol. In addition, CS is generally oriented to a relatively fixed user group. It can perform multi-level verification of permissions, has strong control over information security, and security can be well guaranteed. The BS structure adopts an open structure model of point-to-multipoint and multipoint-to-multipoint.Its security can only be guaranteed by a database of password management on the data server. Moreover, the network security technology is not yet mature, and it is necessary to constantly discover and repair Security breach.

Comparison of user interfaces

The CS structure is mostly built on the Windows platform, the performance methods are limited, and programmers are generally more demanding. The BS structure is built on the browser, and has a richer and more vivid way to communicate with users.

Processing comparison

The CS structure is built on the local area network and deals with a relatively fixed user group in the same area, which meets the high demand for security requirements and is related to the operating system. The BS structure is built on the wide area network, and it deals with different user groups facing scattered areas, and has less relationship with the operating system. In addition, compared with the CS processing mode, the processing mode of the BS simplifies the client and requires only an operating system and a browser to be installed.

Comparison of software reuse

CS structural software can be considered from the inevitable integrity, and the reusability of components is not as good as the reusability built under the BS requirements. BS corresponds to multiple structures and requires the construction of relatively independent functions that can be reused relatively well.

Comparison of system speed

The CS structure is one level less than the BS structure in the logical structure. For the same task, the CS structure is always faster than the BS structure, which makes the CS more conducive to processing large amounts of data. In addition, because the client is directly connected to the server, there is no intermediate link, so the response speed is fast.

Comparison of interactivity and information flow

The CS structure is very interactive. In the CS structure, the client has complete client software, which can process a large number of real-time data streams and respond quickly. Although the BS structure can provide some interactive capabilities, the interactive capabilities are very limited. The information flow of CS is single, while the BS structure can process information such as BB, BC, BG and have changes in the flow direction.