Create a scenario where HTTP is used to retrieve information from a web server. Describe the entire request-response cycle, detailing the role of HTTP headers, status codes, and methods.
### Scenario: Retrieving Weather Data from a Web Server
**Background**: A user wants to check the weather report for their city using a web application. The application sends an HTTP request to a weather API hosted on a web server.
### Step 1: User Action
The user opens their web browser and types in the URL for the weather service, such as `https://api.weather.com/v1/current?city=London`. The browser prepares to send an HTTP GET request to retrieve the current weather data for London.
### Step 2: HTTP Request
The browser constructs an HTTP request:
```
GET /v1/current?city=London HTTP/1.1
Host: api.weather.com
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/90.0.4430.93 Safari/537.36
Accept: application/json
Accept-Language: en-US,en;q=0.9
Connection: keep-alive
```
**Details of the Request:**
- **Method**: `GET` — This method indicates that the client wants to retrieve data from the server.
- **Resource**: `/v1/current?city=London` — This specifies the endpoint and the query parameters for the desired resource.
- **HTTP Version**: `HTTP/1.1` — The version of the HTTP protocol being used.
- **Headers**:
- `Host`: Specifies the server's domain name.
- `User-Agent`: Contains information about the browser and operating system making the request.
- `Accept`: Indicates the type of content the client can process (in this case, JSON).
- `Accept-Language`: Indicates the preferred language for the response.
- `Connection`: Determines whether the network connection should remain open after the transaction.
Once the request is constructed, the browser sends it over the internet to the weather API server.
### Step 3: Server Processing
Upon receiving the HTTP request, the weather API analyzes the request:
1. **URL Parsing**: It identifies the requested resource and query parameters.
2. **Data Retrieval**: The server fetches the current weather data for London from its database.
3. **Response Preparation**: The server generates an HTTP response based on the data retrieved.
### Step 4: HTTP Response
The server constructs an HTTP response:
```
HTTP/1.1 200 OK
Content-Type: application/json
Content-Length: 150
Cache-Control: no-cache
Date: Sat, 01 Apr 2023 12:00:00 GMT
{
"city": "London",
"temperature": "15",
"conditions": "Partly Cloudy"
}
```
**Details of the Response:**
- **Status Line**: `HTTP/1.1 200 OK` —
- `HTTP/1.1`: Version of the HTTP protocol.
- `200`: Status code that indicates the request was successful.
- `OK`: Reason phrase that describes the status code.
- **Headers**:
- `Content-Type`: Indicates that the content being returned is in JSON format.
- `Content-Length`: Specifies the size of the response body in bytes.
- `Cache-Control`: Instructs clients to not cache the response.
- `Date`: Provides the date and time the response was generated.
- **Body**:
- Contains the JSON formatted string with the requested weather information.
### Step 5: Client Receives the Response
The browser receives the HTTP response from the server. It processes the response status:
- **Status Code Check**: The browser checks the status code (200 OK) indicating that the request was successful.
- **Content Handling**: Since the `Content-Type` is `application/json`, the browser parses the JSON data.
### Step 6: Display Data
Finally, the browser renders the weather information to the user in a user-friendly format:
```
Current Weather in London:
- Temperature: 15°C
- Conditions: Partly Cloudy
```
### Conclusion
This entire HTTP request-response cycle demonstrates how a client interacts with a web server to retrieve information. The use of HTTP methods, headers for metadata, and status codes for conveying the result of the request encapsulates the core functionality of web communications.