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The web operates in a cycle of Requests and Responses between the client and the server. In web programming, understanding Request and Response is essential, and these concepts are frequently emphasized. So, what exactly is a Request? What is a Response? Let's delve into the world of Request and Response in web programming through this article.
Understanding HTTP
HTTP stands for Hypertext Transfer Protocol. By using this protocol, the client sends requests to the server, and based on those requests, the server and the web browser provide responses to the client.
In summary, we can say that it forms the basis for one computer (client) to communicate with another computer (server).
What is an HTTP Request?
Once a connection is established using the HTTP protocol between the client and the server, the client sends a Request in binary data to the server to request access to specific files or information.
Each HTTP Request consists of three components: Request Line, Request Header, and Request Body (optional).
● Request Line:
- Specifies the method (GET, POST, PUT, DELETE, …), indicating what the server should do with the information or resource;
- Contains the URL of the used Request to locate resources on the server;
- Specifies the HTTP protocol version (e.g., HTTP/1.0 or HTTP/1.1).
● Request Header: Comprises 0 or more Headers.
Headers are used to convey additional information about the Request, and by utilizing Request Headers, the server knows how to handle the information requested by the client.
For example, consider the Accept-Language field. It informs the server about the client's preferred language, which can be used to respond to the client in their preferred language.
● Request Body: This is an optional component of the HTTP Request
Request Body sends additional information as requested by the server to process the current Request correctly. In the simple example under consideration, the Request sent to the server does not include this Body component.
What is an HTTP Response?
In contrast to HTTP Request, HTTP Response is the package of information sent by the server to the client to provide feedback on the client's previous Request. HTTP Response contains the information requested by the client.
Similar to HTTP Request, HTTP Response also has a similar structure consisting of 3 components: Status Line, Response Header, and Response Body.
● Status Line: Comprises three parts:
- HTTP Version: The version of the HTTP protocol;
- Status Code: The status code;
- Reason Phrase (also known as Status Text): Describes the status.
The status code is a three-digit integer provided by the server to respond to the client's Request. The status code of an HTTP Response is divided into five classes according to the standard, and the class is determined by the first digit of the status code:
- 1xx: Information – Request has been received, continue processing;
- 2xx: Success – Request has been received, understood, and accepted successfully;
- 3xx: Redirection – Additional action is needed to complete the Request;
- 4xx: Client Error – Request contains incorrect syntax or is not executable;
- 5xx: Server Error – The server cannot fulfill a seemingly valid Request.
In the example of the weather web service under consideration, in the Response section, the first line is called Status Line (as shown in the figure below).
The Status Line contains the following information, as visible in the example:
- HTTP Protocol Version: HTTP/1.1;
- Status Code: 200;
- Status Message: OK.
● Response Header: Similar to Request Header, Response Header also contains 0 or more lines of Header. However, it is very rare for a Response to have no Header. These Headers are used to convey additional information to the client.
In the Response Header as shown above, there is a Header named Content-Type. Its value is application/json; charset=utf-8. This means the server is informing the client that the Body part of the Response will contain JSON-formatted data.
● Response Body: Contains the resource data requested by the client.
In the example under consideration, the city of Hyderabad is requesting weather data. Look at the Response Body; it contains information about the weather in this city, such as temperature, humidity, weather description, and some other attributes.
Through this article, I've introduced a simple way to help you understand what Request and Response are in web programming. These are two crucial terms to grasp if you are pursuing a path in developing websites and web applications. I hope the information shared above proves helpful to you!
