The learner can describe the client-server model and put the steps of a single HTTP request/response cycle in order.
Client, server and the request-response cycle
Client, server and the request-response cycle
When you open a website, two sides are involved: the client and the server. The client is any program that sends a request; most often it is a web browser on your laptop or phone. The server is a computer (or a program running on it) that listens for requests, does some work, and sends a response back. Neither side can do the job alone: they communicate through a strict message exchange called the request-response model.
A single cycle looks like this. First the client sends an HTTP request: it states what it wants (a page, an image, some data) and where to find it (a URL). Then the server receives the request, finds or computes the answer, and builds a response. Third, the server sends that response back to the client. Fourth, the client reads the response and shows the result — for example, it renders a web page.
Every response carries two key pieces of information: a status code (a three-digit number that tells the client whether everything went well) and a body (the actual content — HTML, JSON, an image, and so on). Understanding the difference between the status code and the response body is critical for a tester.
As a tester, you can watch this traffic in real time. The browser's developer tools (DevTools) include a Network tab that records every request a page makes and every response it receives. This lets you see exactly what was sent, what came back, and how long it took — without writing a single line of code.
Lesson notes
Client, server and the request-response cycle
When you open a website, two sides are involved: the client and the server. The client is any program that sends a request; most often it is a web browser on your laptop or phone. The server is a computer (or a program running on it) that listens for requests, does some work, and sends a response back. Neither side can do the job alone: they communicate through a strict message exchange called the request-response model.
A single cycle looks like this. First the client sends an HTTP request: it states what it wants (a page, an image, some data) and where to find it (a URL). Then the server receives the request, finds or computes the answer, and builds a response. Third, the server sends that response back to the client. Fourth, the client reads the response and shows the result — for example, it renders a web page.
Every response carries two key pieces of information: a status code (a three-digit number that tells the client whether everything went well) and a body (the actual content — HTML, JSON, an image, and so on). Understanding the difference between the status code and the response body is critical for a tester.
As a tester, you can watch this traffic in real time. The browser's developer tools (DevTools) include a Network tab that records every request a page makes and every response it receives. This lets you see exactly what was sent, what came back, and how long it took — without writing a single line of code.