How does the client server model work?

The client server model is one of the most common architecture concepts in network technology. It regulates the interaction between the client and server. It simplifies everyday tasks such as sending HTTP requests to web servers or transferring files via FTP.

The client server model, also known as the “client server principle”, is a communication model that enables the distribution of tasks within a network.

A server is hardware that provides the necessary resources for other computers or programs but can also be a computer program communicating with the clients. A server accepts the client’s requests, processes them and provides the required response. Different types of clients exist. The computer or a software program communicate with the server. The client sends requests and receives responses from the server. The interaction between server and client is depicted in the client server model.

The client server model has some characteristic features. There is a clear distribution of tasks between the clients and the servers. The server is responsible for providing services. It executes the requested services and delivers the expected response. The client uses and requests the provided services. It thus receives the response from the server

In the client server model, one server serves multiple clients. The server thus processes multiple requests from different clients. To do this, it provides its service permanently and passively. A client actively requests the services from the server and initiates the server tasks.

Here, a physical computer can be both a client and a server. The only decisive factor is its role within a network and whether the computer sends or receives requests for services and resources.

The rules according to which communication between clients and servers takes place are defined in the form of protocols. Depending on the task, different network protocols for data exchange are used. Depending on the area of application, different network types exist.

The concept of distributing tasks and services within a network through the client server model has some pros and cons.

A major pro follows from the central administration. The server is at the center of the network. All users or clients use it. Important resources such as databases are located on the server and centrally accessible. This simplifies administration and maintenance of important resources that require protection. The central location of the server means it’s convenient and low-risk to perform updates.

The central storage of important resources allows for secure and global management of access rights. With sensitive data, it’s important to know who can view data and who’s allowed to manipulate it. In order to protect data, access rights can be set.

The number of clients can be expanded. Several clients work simultaneously using a single server. The clients share the resources of the server. It’s also possible for the server to be located on a different site to the clients. The decisive factor is for the server and clients to be connected via a network. It’s not necessary to have the resources on-site.

Because of centralized attitude and dependency in a client server model, failure of the server leads to the failure of the entire system. If the server is down, the clients no longer function because they can’t receive the necessary responses from the server.

The server performs the resource-intensive tasks. Demands on client resources are significantly lower. If the server has too few resources, this affects all clients. It’s therefore important to choose a provider that reliably provides these resources.

Another factor that shouldn’t be underestimated is the time required to operate your server. In addition to the corresponding know-how, for example, to secure and configure servers, its use requires considerable time investment.

Although the client server model is often used to distribute tasks within networks, there are alternative architectures and concepts.

One alternative is the peer-to-peer model. In this model, a so-called peer program represents servers and clients simultaneously and fulfills both tasks. This model forms the basis of the blockchain.

The primary-secondary model, formerly known as the “master slave model”, is another good example. In this model, the primary part leads the secondary parts and coordinates them. The primary part releases usable resources for the secondary parts and decides when they take over which tasks.

A typical client server application is a web server. Here, the client sends a request to the web server to launch a specific web page. The server sends the requested data back to the client. The web page is displayed in the client’s browser. The Hypertext Transfer Protocol is used for sending HTTP requests.

An email server also works according to the client server principle. When an email client communicates with a server, the client requests and retrieves the emails that are on the server. The server makes the emails available to the client. The protocols used include SMTP, IMAP or POP and TLS.

Another very common application is the transfer of data between a client and web server using the File Transfer Protocols (FTP). This protocol enables uploading and downloading of files.