Exploring Client-Server Architecture: Building Blocks of Modern Applications
Published: 2023-07-04 06:09:06

In this continuously evolving world of software, one architectural style has stood the test of time and remains at the heart of modern applications: client-server architecture. Whether you're a seasoned developer or a curious enthusiast, understanding the fundamentals of client-server architecture is essential for building robust and scalable software solutions.

## What is Client-Server Architecture?

Client-Server architecture is model which delivers functionality of an application into two distinct parts: the client and the server. The client represents the front-end, the user-facing component responsible for interacting with the user. It could be a web browser, a mobile app, or even a desktop application. On the other hand, the server represents the back-end, the behind-the-scenes powerhouse responsible for storing, processing, and managing data.

## How does it work then?


![Client Server Architecture](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/uoo2re1vkm2jk86vgbq9.png)


The client-server architecture or model separates responsibility between clients and servers that are either within the same system or need to communicate over a network.

To access services provided by Server, Client has to request the same over the network and Server will be responding with respective resources/service to client.

Client will have presentation layer and can also have business layer which run GUI and business logic on received response from Server.

On other hand Server will have business logic with data layer running on same machine/computer.

A client-server relationship corresponds to the request-response pattern and should adhere to a standard communications protocol that defines the language and rules used for the communications. The client-server communication adheres to the TCP protocol suite.

To handle business logic for the application, there are different ways the client-server architecture can be setup and handle the request response flow with business logic. Lets have a look at general types of client server architecture

## Types of client-server architecture

### 2-Tier Architecture

![2 Tier Client-Server Architecture](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/uoo2re1vkm2jk86vgbq9.png)

In 2-tier Client Server Architecture, the whole application logic is divided into 2 layers. : the client and the server. Let's take a closer look at each component and how they interact:

- Client:
The client, often a user-facing application, is responsible for presenting the user interface and handling user interactions. It can be a desktop application, a mobile app, or a web browser. The client interacts directly with the end user, gathering input and displaying output. In a 2-tier architecture, the client is also responsible for processing some of the application's business logic.

- Server:
The server component in a 2-tier architecture is primarily responsible for data storage and retrieval. It manages the application's data and handles requests from clients. The server performs any necessary computations or business logic required to process the client's requests. The server typically connects directly to the database or file system to retrieve and update data.

Interaction between the client and server in a 2-tier architecture is straightforward. The client sends a request to the server, which processes the request and returns a response. The client then presents the response to the user.

### 3-Tier Architecture 

![3 Tier Client Server Architecture](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/9rza3ibm9ptdeif2bco7.png)

A 3-tier architecture divides the application into three main layers or tiers, each with its own specific responsibilities. Let's explore each tier and how they interact:

- Client Tier:
Responsible for handling the user interface and user interactions. It can be a web browser, a desktop application, or a mobile app. The primary role of this tier is to present data to the user and capture user inputs. It communicates with the middle tier to request data or perform actions based on user interactions.

- Middle Tier:
The middle tier, also called the application logic tier or business logic tier, acts as an intermediary between the presentation tier and the data tier. It contains the core logic of the application, including processing user inputs, performing business rules, and coordinating data retrieval or storage operations. The middle tier receives requests from the presentation tier, processes them, and interacts with the data tier to retrieve or update data as needed.

- Data Tier:
The data tier, also known as the backend tier, is responsible for managing data storage and retrieval. It includes databases, file systems, or any other persistent storage mechanism. The data tier receives requests from the middle tier and performs operations such as storing, retrieving, updating, or deleting data. It abstracts the underlying data storage details from the other tiers and ensures data integrity and security.


Interaction between the tiers in a 3-tier architecture follows a structured flow. The presentation tier interacts with the middle tier by sending requests for data or actions. The middle tier processes these requests, applies business logic, and communicates with the data tier to fetch or store data. The data tier responds to the middle tier with the requested data or confirmation of successful data operations. The middle tier then processes the response and sends the necessary information back to the presentation tier for display or further actions.

### N-Tier Architecture

![N Tier Architecture](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/1yz2zc5owlf2znvw4z9i.png)


N-tier architecture, also known as multi-tier architecture, is a flexible and scalable model for designing software applications. It divides the application into multiple tiers or layers, each with distinct responsibilities and functions.

It structure on top of same 3-tier architecture where you would have Client, Server and Data tier but apart from these you will also have additional tiers. 

In N-tier architecture, additional tiers can be added depending on the complexity and specific requirements of the application. These tiers can include caching layers, message queues, external services, or any other components that fulfils specific functions within the application's architecture.

## Conclusion

Client-server architecture forms the backbone of modern applications, enabling seamless interaction between clients and servers. By understanding the collaboration and advantages of this architectural style, developers can design and build robust, scalable, and secure software systems. So, whether you're developing a web application, a mobile app, or an enterprise solution, embrace the power of client-server architecture and unlock the potential to create transformative digital experiences.