Client-server facts for kids

A network with one main server.

A peer-to-peer network where computers connect directly.

In the world of computers, client-server is a way that different computer programs work together. It involves two main parts: a client system and a server system. These systems talk to each other over a computer network, or sometimes even on the same computer. Think of it like a restaurant: the client is the customer asking for food, and the server is the chef preparing and giving the food.

A client-server setup helps share the work. The client program always starts the conversation by asking for something. The server program always waits for these requests and then responds.

Another way computers can work together is called peer-to-peer (often shortened to P2P). In a P2P system, every computer can act as both a client and a server at the same time. This means they all have equal roles and responsibilities, unlike the client-server model where one computer is clearly the server. Both client-server and P2P systems are very common today.

The client-server relationship describes how a client asks for a service from a server. The server then receives the request, processes it, and sends the information back to the client. This interaction is a core part of how many computer systems operate.

The most basic client-server setup uses just clients and servers. This is sometimes called a two-tier system. One tier is the client, and the other tier is the server.

The client-server model is a fundamental part of how computers connect and share information. Many everyday applications use this model. For example, when you check your E-mail, browse the internet, or access a database, you are using a client-server system. Your web browser is a client program that connects to web servers all over the world.

What Clients Do

• Clients always start by asking servers for something.
• They wait for the server's reply.
• They receive the information or service back.
• Clients usually connect to only a few servers at a time.
• You, the user, usually interact directly with the client program, often through a graphical user interface (like buttons and menus).

What Servers Do

• Servers are always waiting for requests from clients.
• They fulfill the clients' requests and send the needed data back.
• Sometimes, a server might need to talk to other servers to get all the information for a client's request.
• If more information is needed (like a password), the server might ask the client for it.
• Users typically do not interact directly with a server. They use a client program instead.

Why Client-Server is Good

• Easier Maintenance: In a client-server system, different parts of the computer system can be on separate computers. This makes it easier to fix or update a server without affecting the clients. For example, a server can be repaired or upgraded, and the clients might not even notice.
• Better Security: All the important data is stored on the servers. Servers usually have stronger security controls than individual client computers. This helps make sure that only authorized clients can access and change the data.
• Easier Updates: Since data is stored in one central place (the server), it's much simpler to update that data. In a P2P system, updates might need to be sent to many different computers, which can take a lot of time and lead to errors.
• Works with Many Devices: The client-server model can work with many different types of client devices, even if they have different features.

Challenges of Client-Server

• Network Traffic: If too many clients try to ask a server for things at the same time, the server can get overloaded. This can slow down the network. In a P2P network, adding more computers can actually increase the overall speed, because each computer helps share the load.
• Single Point of Failure: If a server fails, all the clients connected to it might not be able to get the services they need. In P2P networks, the "servers" are spread out among many computers. So, if one or a few computers fail, the rest of the network can often still work and provide the data.

Examples of Clients and Servers

• Common Clients: Your web browser (like Chrome or Firefox), E-mail programs, and online chat apps.
• Common Servers: Web servers (where websites are stored), FTP servers (for file transfers), database servers, E-mail servers, file servers (for shared files), and print servers (for shared printers). Most web services you use are also types of servers.

See also

In Spanish: Cliente-servidor para niños