The lifecycle of a request on an internet browser typically involves the following steps:
User Interaction: The user interacts with the browser by entering a URL in the address bar, clicking on a link, submitting a form, or performing some other action.
DNS Lookup: The browser needs to resolve the domain name of the URL into an IP address. It sends a DNS (Domain Name System) lookup request to a DNS server to obtain the IP address of the server hosting the website.
Establishing a TCP Connection: The browser establishes a TCP (Transmission Control Protocol) connection with the server. This involves a three-way handshake process to ensure a reliable connection between the client and server.
Sending the Request: The browser sends an HTTP (Hypertext Transfer Protocol) request to the server. The request includes the HTTP method (such as GET or POST), the URL, headers (such as cookies or user-agent information), and optionally a request body (for methods like POST).
Server Processing: The server receives the request, processes it, and generates an appropriate response. This may involve accessing a database, running server-side code, or fetching resources from other servers.
Receiving the Response: The browser receives the response from the server, which includes an HTTP status code indicating the success or failure of the request, along with the response body containing the requested content.
Rendering the Web Page: The browser parses the received response, which typically includes HTML, CSS, and JavaScript code. It constructs the Document Object Model (DOM) tree, applies CSS styles, executes JavaScript code, and renders the web page on the user's screen.
Additional Requests: The browser may encounter additional requests within the web page, such as fetching external resources like images, scripts, or stylesheets. It repeats steps 3-7 for each of these additional requests.
Interaction and Updates: The user may interact with the web page, triggering further requests and updates. This can include clicking on links, submitting forms, or making AJAX (Asynchronous JavaScript and XML) requests.
Closing the Connection: After all necessary resources are retrieved and the web page is fully rendered, the browser may keep the TCP connection open for a short time for potential subsequent requests. Otherwise, it closes the connection to free up network resources.
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