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What is the Client-Server model, and how does it work?


Human language:

The client-server model, or client-server architecture - is a distributed application structure, that divides tasks between servers and clients. Client-server architecture typically features multiple users’ workstations, PCs, or other devices, connected to a central server via an Internet connection or other network. The client sends a request for data from a computer or other device, and the server accepts and accommodates the request, sending the data packets back to the user who needs them. In simple words, a client-server model is a networking computing system that partitions tasks or workloads between the providers of a resource or service, called servers, and service requesters, called clients. It describes a specific way devices access the information you store in servers. It also allows multiple clients to open applications or retrieve files from an individual server, which helps maintain consistency across all devices. Many companies across various industries use servers to store and access information, offering more processing power and providing more extensive storage space.

This model can use a local area network (LAN) and a wide area network (WAN).

A local area network (LAN) uses to connect a device to a server using a local path. These connections can be more secure but lack external capabilities. A wide area network (WAN) uses the internet to connect devices and servers. Wide area network (WAN) networks allow for broader applications and access to more significant data collections, although these connections may need reinforcement in security measures.


A Client - is any computer hardware or software device in the home and corporate networks that are capable of receiving information or using a particular service from the service providers (Servers).

Clients or server requesters divides into three types, which are thin, thick, and hybrid clients.

  • Thin clients need a server's resources and processing power to perform many of a device's primary functions.

  • Thick clients are devices that can process large amounts of data and handle multiple tasks without the help of a server.

  • Hybrid clients are devices that can process data within their systems but rely on a server to store data for larger or repeating processing tasks.

A Server - is computer hardware or software that provides functionality to one or many clients, which initiates requests for such services.

Servers are classified by the services they provide. The types of servers are:

  • Database servers: You can use a database server for programs containing highly structured data, like marketing spreadsheets or accounting files.

  • Application servers: These servers help users access internet applications without downloading a copy to their devices.

  • Web servers: These servers exist to facilitate client access to the internet.

  • Computing servers: A computing server provides additional space and power beyond the capabilities of a specific device.

  • Web proxy: A web proxy server acts as a communication gateway between a user and a browser.

  • Domain Name Service (DNS): DNS servers translate what users type into their browser's address bars, allowing the device to locate the website you're searching for on the internet.

A web server serves web pages and a file server serves computer files etc.

Types of Client Server Models:

  • 1-Tier architecture - All-in-One System Consists of a simple program running on a single computer without requiring access to the network. User requests don’t manage any network protocols, therefore the code is simple, and the network is relieved of the extra traffic

  • 2-Tier architecture - Client and Server Consists of the client, the server, and the protocol that links the two tiers. The Graphical User Interface code resides on the client host and the domain logic resides on the server host.

  • 3-Tier architecture - Middleware Consists of a presentation tier, which is the User Interface layer, the application tier, which is the service layer that performs detailed processing, and the data tier, which consists of a database server that stores information

  • N-Tier architecture - Multitier Architecture Divides an application into logical layers, which separate responsibilities and manage dependencies, and physical tiers, which run on separate machines, improve scalability, and add latency from the additional network communication

Communication

The communication between clients and servers is a two-way street that functions through specific Internet protocols: TCP, IP, HTTP, HTTPS, FTP, etc.

A TCP protocol keeps a client-server connection until the completion of a request if the device and server send messages to each other. TCP protocols help organize information into units so that networks can receive, deliver and transfer data efficiently. IP protocols don't require a connection. In an IP protocol, independent data units travel through the internet.

For good inter-process communication, the client and server should have a common language. All communication protocols that define language and rules of communication operate in the application layer of the network model. The exchange of messages between the client and server happens in a request-response messaging pattern.

Once the connection is established, clients can send requests to servers. Requests are typically formatted according to a protocol (such as HTTP, FTP, or SMTP), to maintain compatibility and understanding between both parties. Clients often send requests by entering a URL into a web browser, clicking on a link or button, or using software that sends a query to the server.

After receiving a request from the client, the server processes the request according to the specified protocol. This may involve accessing databases, executing programs, or performing other operations necessary to retrieve the requested data or perform the requested action. The server may also need to communicate with other servers to obtain the required information

After processing the request, the server sends a response back to the client containing the requested data or resources or a status message indicating the result of the operation. Responses are also formatted according to the chosen protocol

Once the client receives the server’s response and the requested data or resources, the connection between the client and server can be closed.

To sum up, we can say that

First, the client sends their request via a network-enabled device; Then, the network server accepts and processes the user's request; Finally, the server delivers the reply to the client.

For a better understanding of the communication between the client and the server, we recommend watching the next video in our course: What is the Client-Server model, and how does it work?


‍Advantages of the Client-Server model:

  • Central access and control of data in a single place;

  • These networks are more secure as all the shared resources are centrally administered;

  • Client-server networks offer effective scalability solutions, allowing organizations to expand their operations;

  • Client-server networks offer better data accessibility through data centralization;

  • Cost-efficient requires less maintenance cost and Data recovery is possible;

  • Data can be accessed efficiently without requiring clients and the server to be in close proximity;

  • A user can easily share resources across various platforms;

  • Load balancing for optimal performance.

Disadvantages of the Client-Server model:

  • If the primary server is not working, the whole model is disrupted;

  • It is more prone to viruses, Trojans, and malware;

  • Multiple users can cause traffic congestion at any time;

  • It needs highly technical stuff for maintaining the network, such as server machines.

Conclusion:

So, if you are asked at an interview: What is the Client-Server model, and how does it work? The best way to answer is:

The client-server model, or client-server architecture - is a distributed application structure, that divides tasks between servers and clients.

Client-server architecture typically features multiple users’ workstations, PCs, or other devices, connected to a central server via an Internet connection or other network. The client sends a request for data from a computer or other device, and the server accepts and accommodates the request, sending the data packets back to the user who needs them.

First, the client sends their request via a network-enabled device; Then, the network server accepts and processes the user's request; Finally, the server delivers the reply to the client.

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