You open a shopping app on your smartphone and search for a product.
The screen appears on your smartphone, while product information, member information, and order records can be managed on servers or other systems.
Many of the digital services we use operate by having user devices and other systems exchange requests and responses.
The first concepts to understand in this structure are client, server, and the Internet.
Clients and servers are distinguished by their roles rather than by device type
When understanding clients and servers, it is easier to focus on the roles they perform when communicating with each other rather than on the form of the device, such as a smartphone, laptop, or computer in a data center.
In the simplest terms:
- The side that sends a request → Client
- The side that receives the request, processes it, and sends back the result → Server
Put simply, the client asks the server, “Please do this,” and the server processes the request and returns, “Here is the result.”
When you open a specific page on a website, the web browser requests, “Show me this page.”
When you search for a product in a shopping app, the app requests, “Find products that match these conditions.”
When you check your account in a banking app, it sends a request such as, “Show me my account information.”
In this way, the side that sends the request is the client, and the side that receives the request and performs the necessary work is the server.
The Internet connects clients and servers
For a client to send a request and a server to return a result, the two systems need to be able to exchange data.
A major communication network that enables this connection is the Internet.
For example, suppose you access an online shopping site from a laptop at home.
Your laptop and the shopping site’s server may be in different locations. The shopping site’s server may be operating in a data center in another region.
A request sent from the laptop travels to the server through the Internet, and the result processed by the server returns to the laptop through the Internet.
The structure can be expressed simply as follows.
Client → Internet → Server
The result then travels in the opposite direction.
Client ← Internet ← Server
The Internet is a communication network that carries requests and results between clients and servers.
It delivers the client’s request to the server and carries the server’s response back to the client.
Requests and responses show how digital services work
Consider a situation where you search for laptop on an online shopping site.
1. The user enters a search term
The user enters laptop into the search box of a smartphone app or web browser.
The app or web browser receives the user’s input and prepares to request the necessary task from the server.
At this point, the side sending the request is the client.
2. The client sends a request to the server
The client sends a request to the server asking it to “find products related to laptops.”
In computer communication, asking for a task or information in this way is called a request.
3. The request travels to the server through the Internet
The request created by the client travels through the Internet to the shopping site’s server.
When the user presses the search button, the request data travels across the network to the server.
4. The server processes the request
The server checks what kind of request it has received.
For a search request, it finds the necessary product information and creates results that match the search conditions.
During this process, the server may also request additional information from a database or another system.
Depending on the service structure, the server connects to systems such as databases, storage, and authentication systems to retrieve the necessary information and create the result.
5. The server returns the result
Once the search results are ready, the server sends them to the client.
The result that the server sends back in response to a request is called a response.
6. The client displays the result on the screen
The response sent by the server travels back to the user’s device through the Internet.
The client displays the received data, such as product names, prices, and images, on the screen.
The user presses the search button and sees a list of products. In between, the following flow takes place.
User input → Client request → Transmission through the Internet → Server processing → Server response → Transmission through the Internet → Display on the client screen
This request-and-response structure is commonly used in many digital services, including websites, shopping apps, banking apps, and messaging services.
The same device can act as either a client or a server
Once clients and servers are understood as roles, it becomes easier to understand how the same device can perform different roles depending on the situation.
For example, when you access a website from your laptop, the web browser running on the laptop sends a request to the server.
In this situation, your laptop side performs the client role.
If you run a program on your laptop that receives and processes requests from other devices, your laptop can perform the server role while processing those requests.
Devices such as smartphones, laptops, and desktop computers can perform client and server roles depending on the service structure.
Who sends the request and who receives and processes that request is the basis for distinguishing clients from servers.
Where do companies manage their servers?
A personal laptop can technically perform a server role.
Companies that operate online services use server environments suited to their scale and operating requirements.
Some internal systems may be used by dozens of people, while other services may be used by hundreds of thousands or millions of people at the same time.
To operate these services, servers need to process large numbers of requests reliably.
They need a stable supply of power for long-term operation and a cooling environment to handle the heat generated by servers. Network infrastructure for exchanging data with external systems and security systems for protecting the service are also configured together.
Companies can operate servers in different environments depending on their scale and needs.
- Internal server room
- A company can place servers inside an office or business facility and manage them directly.
- Private data center
- A company can build its own data center to operate large numbers of servers and network equipment.
- External data center
- A company can operate its own servers while using the space, power, and network environment provided by a professional data center operator.
- Cloud
- A company can configure and operate server functions using computing resources provided by a cloud provider.
A company’s digital services operate using servers together with infrastructure such as networks, power, cooling, and security.
Viewed more broadly, these foundations connect to the digital infrastructure discussed earlier.
DANA NOTES in One Line
Clients and servers are distinguished by their roles in sending and processing requests, while the Internet is the communication network that enables the two sides to exchange data.
